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October

October

October is the tenth month of the year in the Gregorian Calendar and one of seven Gregorian months with the length of 31 days. October begins (astrologically) with the sun in the sign of Libra and ends in the sign of Scorpio. Astronomically speaking, the sun begins in the constellation of Virgo and ends in the constellation of Libra. The name is from the Latin Word "octo" for "eight". October was the eighth month in the Roman calendar until a monthless winter period (summer in the southern hemisphere) was divided between January and February.

Events in October

February
- Major League Baseball Playoffs
- National Coming Out Day
- National Breast Cancer Awareness Month
- Second Monday of the month: Thanksgiving in Canada, Columbus Day in the USA.
- The European Union and the USA revert back from Summer Time (Daylight Saving Time) to regular zone time on the last Sunday of the month, from 3 AM to 2 AM. At Merton College, Oxford, this has been celebrated since 1972 with a backward procession round Fellow's Quad between 2 A.M. BST and 2 A.M. GMT.
- Filipino-American History Month
- The last Monday in October is one of the public holidays in the Republic of Ireland and in the Irish Calendar the month is called Deireadh Fómhair (literally "End of Autumn") and is the third and last month of the Autumn season.
- Oktober Fest in Germany
- Halloween on the night of 31 October to 1 November
- In the pagan wheel of the year October ends at or near to Samhain in the northern hemisphere and Bealtaine in the southern hemisphere.
- The Russian October Revolution of 1917 (which took place on November 7 in the Gregorian Calendar).
- The October Crisis of 1970 in Quebec, Canada.

Trivia

- October begins on the same day of the week as January in common years, but no other month begins on the same day of the week as October in leap years.
- October's flower is the calendula.
- October's birthstone is opal or tourmaline.
- October is also the name of an album and song by U2.

Other names

- In Czech, October is called říjen. The origin of this name is in the deer's belling in this month.
- A traditional Dutch name for October is Wijnmaand (wine month) because the first wines of the year have ripened.
- In Finnish, October is called lokakuu, meaning "month of dirt".
- In Scottish Gaelic, October is called an Damhar, meaning "rutting time" (of stags).
- In Irish, October is called Deireadh Fómhair, meaning "end of harvest-time".
- In Turkish, October is called Ekim, meaning "sowing" because of the sowing of wheat.
- In the old Japanese calendar, the month is called Kan'na dzuki (神無月), meaning the absence of god.

Tenth

Tenth could refer to:
- In mathematics, arithmetic or plain old numbers a tenth is one part of a unit or one divided equally into ten parts. A tenth is the reciprocal of ten. A tenth is written as a decimal fraction thus 0.1 and as a vulgar fraction as 1/10.
- Tenth is also the ordinal number, being occurrence number ten, following ninth and preceding eleventh. The ordinal number tenth is written 10th.
- In music or music theory a tenth is the note ten scale degrees from the root of chord and also the interval between the root and the tenth.
- In music a tenth is a compound third.

Month

:In Egyptian mythology, Month is an alternate spelling for Menthu. A month is that from one date to the next months date with the same number. so Emma's wrong. The month is a unit of time, used with calendars, which is approximately as long as some natural period related to the motion of the Moon (moon gives month in the same way that wide gives width and broad gives breadth). The traditional concept arose with the cycle of moon phases; such months are synodic months and last ~29.53 days. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months are still the basis of many calendars.

Astronomical background

The motion of the Moon in its orbit is very complicated and its period is not constant. Moreover, many cultures (most notably those using the ancient Hebrew (Jewish) calendar and the Islamic calendar) start a month with the first appearance of the thin crescent of the new moon after sunset over the western horizon. The date and time of this actual observation depends on the exact geographical longitude as well as latitude, atmospheric conditions, the visual acuity of the observers, etc. Therefore the beginning and lengths of months in these calendars can not be accurately predicted. Most Jews currently follow a precalculated calendar, but the Karaites rely on actual moon observations.

Sidereal month

The actual period of the Moon's orbit as measured in a fixed frame of reference is known as a sidereal month, because it is the time it takes the Moon to return to the same position on the celestial sphere among the fixed stars (Latin: sidus): 27.321 661 days (27d 7h 43min 11.5sec) or about 27 ⅓ days. This type of "month" has appeared among cultures in the Middle East, India, and China in the following way: they divided the sky in 27 or 28 lunar mansions, characterized by asterisms (apparent groups of stars), one for each day that the Moon follows its track among the stars.

Tropical month

It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of precession, this point moves back slowly along the ecliptic. Therefore it takes the Moon less time to return to an ecliptic longitude of zero than to the same point amidst the fixed stars: 27.321 582 days (27d 7h 43min 4.7sec). This slightly shorter period is known as tropical month; cf. the analogous tropical year of the Sun.

Anomalistic month

Like all orbits, the Moon's orbit is an ellipse rather than a circle. However, the orientation (as well as the shape) of this orbit is not fixed. In particular, the position of the extreme points (the line of the apsides: perigee and apogee), makes a full circle in about nine years. It takes the Moon longer to return to the same apsis because it moved ahead during one revolution. This longer period is called the anomalistic month, and has an average length of 27.554 551 days (27d 13h 18min 33.2sec), or about 27 ¹/₂ days. The apparent diameter of the Moon varies with this period, and therefore this type of month has some relevance for the prediction of eclipses (see saros), whose extent, duration, and appearance (whether total or annular) depend on the exact apparent diameter of the Moon. The apparent diameter of the full moon varies with the full moon cycle which is the beat period of the synodic and anomalistic month, and also the period after which the apsides point to the Sun again.

Draconic month

The orbit of the Moon lies in a plane that is tilted with respect to the plane of the ecliptic: it has an inclination of about five degrees. The line of intersection of these planes defines two points on the celestial sphere: the ascending and descending nodes. The plane of the Moon's orbit precesses over a full circle in about 18.6 years, so the nodes move backwards over the ecliptic with the same period. Hence the time it takes the Moon to return to the same node is again shorter than a sidereal month: this is called the draconic, nodical, or draconitic month. It lasts 27.212 220 days (27d 5h 5min 35.8sec), or about 27 ⅕ days. It is important for predicting eclipses: these take place when the Sun, Earth and Moon are on a line. Now (as seen from the Earth) the Sun moves along the ecliptic, while the Moon moves along its own orbit that is inclined on the ecliptic. The three bodies are only on a line when the Moon is on the ecliptic, i. e. when it is at one of the nodes. The "draconic/draconitic" month refers to the mythological dragon that lives in the nodes and regularly eats the Sun or Moon during an eclipse.

Synodic month

The cause of moon phases is that from the Earth we see the part of the Moon that is illuminated by the Sun from different angles as the Moon traverses its orbit. So the appearance depends on the position of the Moon with respect to the Sun (as seen from the Earth). Because the Earth orbits the Sun, it takes the Moon extra time (after completing a sidereal month, i. e. a full circle) to catch up and return to the same position with respect to the Sun. This longer period is called the synodic month (from Greek syn hodô or σὺν ὁδῴ, with the way, i. e. the Moon travelling with the Sun). Because of the perturbations of the orbits of the Earth and Moon, the actual time between lunations may range from about 29.27 to about 29.83 days. The long-term average duration is 29.530 588 days (29d 12h 44min 2.8sec), or about 29 ½ days.

Month lengths

Here is a list of the average length of the various astronomical lunar months . These are not constant, so a first-order (linear) approximation of the secular change is provided: Valid for the epoch J2000.0 (1 Jan. 2000 12:00 TT): Note: time expressed in Ephemeris Time (more precisely Terrestrial Time) with days of 86400 SI seconds. y is years since the epoch (2000), expressed in Julian years of 365.25 days. Note that for calendrical calculations, one would probably use days measured in the time scale of Universal Time, which follows the somewhat unpredictable rotation of the Earth, and progressively accumulates a difference with ephemeris time called ΔT.

Calendrical consequences

:For more details on this topic, see lunar calendar and lunisolar calendar. At the simplest level, all lunar calendars are based on the approximation that 2 lunations last 59 days: 30 day full month followed by a 29 day hollow month — but this is only marginally accurate and quickly needs correction by using larger cycles, or the equivalent of leap days. Second, the synodic month does not fit easily into the year, which makes constructing accurate, rule-based lunisolar calendars difficult. The most common solution to this problem is the Metonic cycle, which takes advantage of the fact that 235 lunations are approximately 19 tropical years (which add up to not quite 6940 days). However, a Metonic calendar (such as the Hebrew calendar) will drift against the seasons by about 1 day every 200 years. The problems of creating reliable lunar calendars may explain why solar calendars, having months which no longer relate to the phase of the moon, and being based only on the more predictable motion of the sun against the sky, have generally replaced lunar calendars for civil use in most societies.

Months in various calendars

Julian and Gregorian calendars

The Gregorian calendar, like the Julian calendar before it, has twelve months: #January, 31 days #February, 28 days, 29 in leap years, or 30 on certain occasions in related calenders #March, 31 days #April, 30 days #May, 31 days #June, 30 days #July, 31 days #August, 31 days #September, 30 days #October, 31 days #November, 30 days #December, 31 days For the rationale behind the unusual day lengths, see February and August. One of Wikipedia's sister projects, Wiktionary, provides translations of each of the Gregorian/Julian calendar months into a dozen or more languages. Month-by-month links are provided here: January, February, March, April, May, June, July, August, September, October, November, December. Months existing in the Roman calendar in the past include:
- Mercedonius, an occasional month after February to realign the calendar.
- Quintilis, renamed to July in honor of Julius Caesar.
- Sextilis, renamed to August in honor of Caesar Augustus. The famous mnemonic Thirty days hath September is the most common way of teaching the lengths of the months.

Islamic calendar

There are also twelve months in the Islamic calendar. They are named as follows: # Muharram ul Haram (or shortened to Muharram) محرّم # Safar صفر # Rabi`-ul-Awwal (Rabi' I) ربيع الأول # Rabi`-ul-Akhir (or Rabi` al-THaany) (Rabi' II) ربيع الآخر أو ربيع الثاني # Jumaada-ul-Awwal (Jumaada I) جمادى الأول # Jumaada-ul-Akhir (or Jumaada al-THaany) (Jumaada II) جمادى الآخر أو جمادى الثاني # Rajab رجب # Sha'aban شعبان # Ramadhan رمضان # Shawwal شوّال # Dhul Qadah ذو القعدة (or Thw al-Qi`dah) # Dhul Hijja ذو الحجة (or Thw al-Hijjah) For details, please see Islamic calendar.

Hebrew Calendar

The Hebrew calendar has 12 or 13 months. # Nisan, 30 days # Iyyar, 29 days # Sivan, 30 days # Tammuz, 29 days # Av, 30 days # Elul, 29 days # Tishri, 30 days # Heshvan, 29/30 days # Kislev, 29/30 days # Tevet, 29 days # Shevat, 30 days # Adar 1, 30 days, intercalary month # Adar 2, 29 days Adar 1 is only added in leap years. In ordinary years, Adar 2 is simply called Adar.

Hindu Calendar

The Hindu Calendar has various systems of naming the months. The months in the lunar calendar are: # Chaitra # Vaishaakha # Jyaishtha # Aashaadha # Shraavana # Bhaadrapada # Aashvayuja # Kaartika # Maargashiirsha # Pausha # Maagha # Phaalguna These are also the names used in the Indian national calendar for the newly redefined months. The names in the solar calendar are just the names of the zodiac sign in which the sun travels. They are # Mesha # Vrishabha # Mithuna # Kataka # Simha # Kanyaa # Tulaa # Vrishcika # Dhanus # Makara # Kumbha # Miina

Iranian/Persian calendar

The Iranian / Persian calendar, currently used in Iran and Afghanistan, also has 12 months. The Persian names are included in the parentheses. # Farvardin (فروردین)‎, 31 days # Ordibehesht (اردیبهشت)‎, 31 days # Khordad (خرداد)‎, 31 days # Tir (تیر)‎, 31 days # Mordad (مرداد)‎, 31 days # Shahrivar (شهریور)‎, 31 days # Mehr (مهر)‎, 30 days # Aban (آبان)‎, 30 days # Azar (آذر)‎, 30 days # Dey (دی)‎, 30 days # Bahman (بهمن)‎, 30 days # Esfand (اسفند)‎, 29 days, 30 in leap years

Icelandic/Old Norse calendar

The old icelandic calendar is not in official use anymore, but some holidays and annual feasts are still calculated according to it in Iceland. It has 12 months, broken down into two groups of six.
- Skammdegi (e. Short days) # Gormánuður (14. October - 13. November, e. slaughter month or Gór's month) # Ýlir (14. November - 13. December, e. Yule month) # Mörsugur (14. December - 12. January, e. fat sucking month) # Þorri (13. January - 11. February, e. frozen snow month) # Góa (12. February - 13. march, e. Góa's month, see Nór) # Einmánuður (14. march - 13. April, e. lone or single month)
- Náttleysi (e. Nightless days) # Harpa (14. April - 13. may, Harpa is a female name, probably a forgotten goddess) # Skerpla (14. may - 12. June, another forgotten goddess) # Sólmánuður (13. June - 12. July, e. sun month) # Heyannir (13. July - 14. August, e. hay business month) # Tvímánuður (15. August - 14. September, e. two or second month) # Haustmánuður (15. September - 13. October, e. autumn month)

Notes

# Derived from ELP2000-85: M. Chapront-Touzé, J. Chapront (1991): Lunar tables and programs from 4000 B. C. to A. D. 8000. Willmann-Bell, Richmond VA; ISBN 0-943396-33-6

Year

A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. By extension, this can be applied to any planet: for example, a "Martian year" is a year on Mars.

Seasonal year

A seasonal year is the time between successive recurrences of a seasonal event such as the flooding of a river, the migration of a species of bird, the flowering of a species of plant, the first frost, or the first scheduled game of a certain sport. All of these events can have wide variations of more than a month from year to year.

Calendar year

A calendar year is the time between two dates with the same name in a calendar. Solar calendars usually aim to predict the seasons, but because the length of individual seasonal years varies significantly, they instead use an astronomical year as a surrogate. For example, the ancient Egyptians used the heliacal rising of Sirius to predict the flooding of the Nile. The Gregorian calendar aims to keep the vernal equinox on or close to March 21; hence it follows the vernal equinox year. The average length of its year is 365.2425 days. No astronomical year has an integer number of days or months, so any calendar that follows an astronomical year must have a system of intercalation such as leap years. In the formerly used Julian calendar, the average length of a year was 365.25 days. This is still used as a convenient time unit in astronomy, see below.

Astronomical years

Julian year

The Julian year, as used in astronomy and other sciences, is a time unit defined as exactly 365.25 days. This is the normal meaning of the unit "year" (symbol "a" from the Latin annus, annata) used in various scientific contexts. The Julian century of 36525 days and the Julian millennium of 365250 days are used in astronomical calculations. Fundamentally, expressing a time interval in Julian years is a way to precisely specify how many days (not how many "real" years), for long time intervals where stating the number of days would be unwieldy and unintuitive.

Sidereal year

The sidereal year is the time for the Earth to complete one revolution of its orbit, as measured in a fixed frame of reference (such as the fixed stars, Latin sidus). Its duration in SI days of 86,400 SI seconds each is on average: :365.256 363 051 days (365 d 6 h 9 min 9 s) (at the epoch J2000.0 = 2000 January 1 12:00:00 TT).

Tropical year

A tropical year is the time for the Earth to complete one revolution with respect to the framework provided by the intersection of the ecliptic (the plane of the orbit of the Earth) and the plane of the equator (the plane perpendicular to the rotation axis of the Earth). Because of the precession of the equinoxes, this framework moves slowly westward along the ecliptic with respect to the fixed stars (with a period of about 26,000 tropical years); as a consequence, the Earth completes this year before it completes a full orbit as measured in a fixed reference frame. Therefore a tropical year is shorter than the sidereal year. The exact length of a tropical year depends on the chosen starting point: for example the vernal equinox year is the time between successive vernal equinoxes. The mean tropical year (averaged over all ecliptic points) is: :365.242 189 67 days (365 d 5 h 48 min 45 s) (at the epoch J2000.0).

Anomalistic year

The anomalistic year is the time for the Earth to complete one revolution with respect to its apsides. The orbit of the Earth is elliptical; the extreme points, called apsides, are the perihelion, where the Earth is closest to the Sun (January 2 in 2000), and the aphelion, where the Earth is farthest from the Sun (July 2 in 2000). Because of gravitational disturbances by the other planets, the shape and orientation of the orbit are not fixed, and the apsides slowly move with respect to a fixed frame of reference. Therefore the anomalistic year is slightly longer than the sidereal year. It takes about 112,000 years for the ellipse to revolve once relative to the fixed stars. The anomalistic year is also longer than the tropical year (which calendars attempt to track) and so the date of the perihelion gradually advances every year. It takes about 21,000 years for the ellipse to revolve once relative to the vernal equinox, thus for the date of perihelion to return to the same place (given a calendar that tracks the seasons perfectly). The average duration of the anomalistic year is: :365.259 635 864 days (365 d 6 h 13 min 52 s) (at the epoch J2000.0).

Draconic year

The draconitic year, eclipse year or ecliptic year is the time for the Sun (as seen from the Earth) to complete one revolution with respect to the same lunar node (a point where the Moon's orbit intersects the ecliptic). This period is associated with eclipses: these occur only when both the Sun and the Moon are near these nodes; so eclipses occur within about a month of every half eclipse year. Hence there are two eclipse seasons every eclipse year. The average duration of the eclipse year is: :346.620 075 883 days (346 d 14 h 52 min 54 s) (at the epoch J2000.0). :This term is sometimes also used to designate the time it takes for a complete revolution of the Moon's ascending node around the ecliptic: 18.612 815 932 years (6798.331 019 days).

Fumocy

The full moon cycle or fumocy is the time for the Sun (as seen from the Earth) to complete one revolution with respect to the perigee of the Moon's orbit. This period is associated with the apparent size of the full moon, and also with the varying duration of the anomalistic month. The duration of one full moon cycle is: :411.784 430 29 days (411 d 18 h 49 min 34 s) (at the epoch J2000.0).

Heliacal year

A heliacal year is the interval between the heliacal risings of a star. It equals the sidereal year only if the star is on the ecliptic. It differs from the sidereal year for stars north or south of the ecliptic because of the significant angle (23.5°) between Earth's celestial equator and the ecliptic.

Sothic year

The Sothic year is the interval between heliacal risings of the star Sirius. Its duration is very close to the mean Julian year of 365.25 days.

Gaussian year

The Gaussian year is the sidereal year for a planet of negligible mass (relative to the Sun) and unperturbed by other planets that is governed by the Gaussian gravitational constant. Such a planet would be slightly closer to the Sun than Earth's mean distance. Its length is: :365.256 898 3 days (365 d 6 h 9 min 56 s).

Besselian year

The Besselian year is a tropical year that starts when the fictitious mean Sun reaches an ecliptic longitude of 280°. This is currently on or close to 1 January. It is named after the 19th century German astronomer and mathematician Friedrich Bessel. An approximate formula to compute the current time in Besselian years from the Julian day is: :B = 2000 + (JD - 2451544.53)/365.242189

Great year

The Great year, Platonic year, or Equinoctial cycle corresponds to a complete revolution of the equinoxes around the ecliptic. Its length is approximately 25,770.639 22 years (9,412,725 d 23 h 22 min).

Variation in the length of the year and the day

The exact length of an astronomical year changes over time. The main sources of this change are: #The precession of the equinoxes changes the position of astronomical events with respect to the apsides of Earth's orbit. An event moving toward perihelion recurs with a decreasing period from year to year; an event moving toward aphelion recurs with an increasing period from year to year. #The gravitational influence of the Moon and planets changes the shape of the Earth's orbit. Tidal drag between the Earth and the Moon and Sun increases the length of the day and of the month. This in turn depends on factors such as continental rebound and sea level rise. It is also suspected that changes in the effective mass of the sun, caused by nuclear fusion, could have a significant impact on the earth year over time.

Summary of various kinds of year

- 353, 354 or 355 days — the lengths of regular years in some lunisolar calendars
- 354.37 days — 12 lunar months; the average length of a year in lunar calendars
- 365 days — a common year in many solar calendars; ~31.53 million seconds
- 365.24219 days — a mean tropical year near the year 2000
- 365.2424 days — a vernal equinox year.
- 365.2425 days — the average length of a year in the Gregorian calendar
- 365.25 days — the average length of a year in the Julian calendar; the light year is based on it; it is 31,557,600 seconds
- 365.2564 days — a sidereal year
- 366 days — a leap year in many solar calendars; 31.62 million seconds
- 383, 384 or 385 days — the lengths of leap years in some lunisolar calendars
- 383.9 days — 13 lunar months; a leap year in some lunisolar calendars An average Gregorian year is 365.2425 days = 52.1775 weeks, 8,765.82 hours = 525,949.2 minutes = 31,556,952 seconds (mean solar, not SI). A common year is 365 days = 8,760 hours = 525,600 minutes = 31,536,000 seconds. A leap year is 366 days = 8,784 hours = 527,040 minutes = 31,622,400 seconds. An easy to remember approximation for the number of seconds in a year is

\begin\pi\end

×10⁷ seconds. The 400-year cycle of the Gregorian calendar has 146097 days and hence exactly 20871 weeks. See also Numerical facts about the Gregorian calendar.

Day

:The Day language is spoken in Chad. A day (symbol: d) is a unit of time. It is not an SI unit but it is accepted for use with SI. The SI unit of time is the second. It has several definitions.

Definition of a day in SI

There is one day for every 86,400 SI seconds.

Definition of a day in astronomy

For a given planet, there are two types of day defined in astronomy: 1 apparent sidereal day = a single rotation of a planet with respect to the distant stars (for Earth it is 23.934 solar hours or 24 sidereal hours) 1 solar day = a single rotation of a planet with respect to Sun.

Origin

The term comes from the Old English dæg, with similar terms common in all other Indo-European languages, such as dies in Latin and dive in Sanskrit.

Colloquial definition of day

The word refers either to the period of light when the Sun is above the local horizon or to the full day covering a dark and a light period. The latter is sometimes called a nychthemeron in English, from the Greek for night-day. Greek painting by Peter Nicolai Arbo.]]

Introduction

Different definitions of the day are based on the apparent motion of the Sun across the sky (solar day; see solar time). The reason for this apparent motion is the rotation of the Earth around its axis, as well as the revolution of the Earth in its orbit around the Sun. A day, as opposed to night, is commonly defined as the period during which sunlight directly reaches the ground, assuming that there are no local obstacles. Two effects make days on average longer than nights. The Sun is not a point, but has an apparent size of about 32 minutes of arc. Additionally, the atmosphere refracts sunlight in such a way that some of it reaches the ground even when the Sun is below the horizon by about 34 minutes of arc. So the first light reaches the ground when the centre of the Sun is still below the horizon by about 50 minutes of arc. The difference in time depends on the angle at which the Sun rises and sets (itself a function of latitude), but amounts to almost seven minutes at least. Ancient custom has a new day start at either the rising or setting of the Sun on the local horizon (Italian reckoning, for example). The exact moment of, and the interval between, two sunrises or two sunsets depends on the geographical position (longitude as well as latitude), and the time of year. This is the time as indicated by ancient hemispherical sundials. A more constant day can be defined by the Sun passing through the local meridian, which happens at local noon (upper culmination) or midnight (lower culmination). The exact moment is dependent on the geographical longitude, and to a lesser extent on the time of the year. The length of such a day is nearly constant (24 hours ± 30 seconds). This is the time as indicated by modern sundials. A further improvement defines a fictitious mean Sun that moves with constant speed along the celestial equator; the speed is the same as the average speed of the real Sun, but this removes the variation over a year as the Earth moves along its orbit around the Sun (due to both its velocity and its axial tilt). The Earth's day has increased in length over time. The original length of one day, when the Earth was new about 4.5 billion years ago, was about six hours as determined by computer simulation. It was 21.9 hours 620 million years ago as recorded by rhythmites (alternating layers in sandstone). This phenomenon is due to tides raised by the Moon which slow Earth's rotation. Because of the way the second is defined, the mean length of a day is now about 86,400.002 seconds, and is increasing by about 1.7 milliseconds per century (an average over the last 2700 years). See tidal acceleration for details.

Civil day

For civil purposes a common clock time has been defined for an entire region based on the mean local solar time at some central meridian. Such time zones began to be adopted about the middle of the 19th century when railroads with regular schedules came into use, with most major countries having adopted them by 1929. For the whole world, 39 such time zones are now in use. The main one is "world time" or UTC (Coordinated Universal Time). The present common convention has the civil day starting at midnight, which is near the time of the lower culmination of the mean Sun on the central meridian of the time zone. A day is commonly divided into 24 hours of 60 minutes of 60 seconds each.

Leap seconds

In order to keep the civil day aligned with the apparent movement of the Sun, leap seconds may be inserted. A civil clock day is typically 86400 SI seconds long, but will be 86401 s long in the event of a leap second. Leap seconds are announced in advance by the International Earth Rotation and Reference Systems Service which measures the Earth's rotation and determines whether a leap second is necessary. Leap seconds occur only at the end of a UTC month, and have only ever been inserted at the end of June 30 or December 31.

Astronomy

In astronomy, the sidereal day is also used; it is about 3 minutes 56 seconds shorter than the solar day, and close to the actual rotation period of the Earth, as opposed to the Sun's apparent motion. In fact, the Earth spins 366 times about its axis during a 365-day year, because the Earth's revolution about the Sun removes one apparent turn of the Sun about the Earth.

Boundaries of the day

For most diurnal animals, including Homo sapiens, the day naturally begins at dawn and ends at sunset. Humans, with our cultural norms and scientific knowledge, have supplanted Nature with several different conceptions of the day's boundaries. The Jewish day begins at either sunset or at nightfall (when three second-magnitude stars appear). Medieval Europe followed this tradition, known as Florentine reckoning: in this system, a reference like "two hours into the day" meant two hours after sunset and thus times during the evening need to be shifted back one calendar day in modern reckoning. Days such as Christmas Eve, Halloween, and the Eve of Saint Agnes are the remnants of the older pattern when holidays began the evening before. Present common convention is for the civil day to begin at midnight, that is 00:00, and last a full twenty-four hours until the next 00:00 (also known as 24:00, but this is not as widely used). In ancient Egypt the day was reckoned from sunrise to sunrise. Muslims fast from dawn (traditionally when a white thread can be distinguished from a black thread) to sunset each day of the month of Ramadan. In the United States, nights are named after the previous day, e.g. "Friday night" usually means the entire night between Friday and Saturday. This is the opposite of the Jewish pattern. This difference from the civil day often leads to confusion. Events starting at midnight are often announced as occurring the day before. TV-guides tend to list nightly programs at the previous day, although programming a VCR requires the strict logic of starting the new day at 00:00 (to further confuse the issue, VCRs set to the 12-hour clock notation will label this "12:00 AM"). Expressions like "today", "yesterday" and "tomorrow" become ambiguous during the night. Validity of tickets, passes, etc., for a day or a number of days may end at midnight, or closing time, when that is earlier. However, if a service (e.g. public transport) operates from e.g. 6:00 to 1:00, the last hour may well count as being part of the previous day (also for the arrangement of the timetable). For services depending on the day ("closed on Sundays", "does not run on Fridays", etc.) there is a risk of ambiguity. As an example, for the Dutch Railways, a day ticket is valid 28 hours, from 0:00 to 4:00 the next night.

List of famous days

- Black Monday
- Black Friday
- Bloody Sunday
- D-Day
- The Day The Music Died
- Ides of March
- Judgement Day
- September 11, 2001 See also List of commemorative days

People named Day

Some noted people with the name Day include Doris Day, Stockwell Day, and Dorothy Day.

External links

- [http://www.fourmilab.ch/cgi-bin/uncgi/Earth/action?opt=-p&img=learth.evif Show where it is daytime at the moment]
- [http://ptaff.ca/soleil/?lang=en_CA Sunrise and sunset, all year long, anywhere] Category:Units of time als:Tag ko:일 (시간) ja:日 simple:Day th:วัน

Libra

:This article is about the constellation. Libra is also a Roman coin and weight measure, see Ancient Roman weights and measures. Libra is also a novel by Don DeLillo. LIBRA is also a political party in Croatia. Libra is also an album by Toni Braxton. Libra (20px, and Latin for balance) is a constellation of the zodiac. It is a fairly inconspicuous constellation and has no star of first magnitude, lying between Virgo to the west and Scorpius to the east. As the names of the brighter stars testify, it was at one point part of Scorpius' claws.

Notable features

The brightest stars in Libra form a rectangle:
- α Librae, Zubenelgenubi ("southern claw"), a visual binary;
- β Librae, Zubeneschamali ("northern claw");
- γ Librae, Zubenelakrab ("scorpion's claw");
- σ Librae, an eclipsing variable. α and β Librae are the scales' balance beam, and γ and σ are the weighing pans. σ Librae was formerly known as γ Scorpii despite being well inside the boundaries of Libra. It was not redesignated as σ Librae until 1851 (by Benjamin A. Gould).

Mythology

The constellation, which had originally formed part of the claws of the scorpion (Scorpio), is the youngest of the Zodiac and the only one not to represent a living creature. In later Greek mythology, the constellation, which when considered on its own looks vaguely like a set of scales, was considered to depict the scales held by Astraea (identified as Virgo), the goddess of justice. Since Libra was originally part of Virgo (as scales), and before that part of Scorpio, it was not a distinct entity for which a zodiac sign was named. Its place may have been taken by Boötes, which is the nearest to the ecliptic. Since the place Boötes should have held on the ecliptic is vacant, it may have, together with Ursa Major, Draco, and Ursa Minor, also in Libra, led to the myth of the apples of the Hesperides, one of The Twelve Labours of Herakles.

Astrology

The Western astrological sign Libra of the tropical zodiac (September 23–October 22) differs from the astronomical constellation and the Hindu astrological sign of the sidereal zodiac (October 31–November 22). In some cosmologies, Libra is associated with the classical element Air, and thus called an Air Sign (with Aquarius and Gemini). It is also one of the four cardinal signs (along with Aries, Cancer, and Capricorn). Its polar opposite is Aries. It is the domicile of Venus and the exaltation of Saturn. Each astrological sign is assigned a part of the body, viewed as the seat of its power. Libra rules the lower back and internal reproductive organs. The symbol for Libra is the Scales.

Stars

:Stars with proper names: :
- (α Lib) Zubenelgenubi [Zuben Elgenubi] or Kiffa Australis [Elkhiffa australis] (8/α¹ Lib, 9/α² Lib) – double 5.15, 2.75 :
- : < الزبن الجنوبي az-zuban al-janūbiyy The southern claw (of the scorpion) :
- : < ? al-kiffah al-janūbiyy The southern pan (of the scales) :
- (27/β Lib) 2.61 Zubeneschamali [Zuben Eschamali, Zuben el Chamali, Zubenesch, Zubenelg] or Kiffa Borealis :
- : < الزبن الشمالي az-zuban aš-šamāliyy The northern claw (of the scorpion) :
- : < ? al-kiffah aš-šamāliyy The northern pan (of the scales) :
- (38/γ Lib) 3.91 Zuben Elakrab [Zuben (el) Hakrabi, Zuben Hakraki] :
- : < زبن العقرب zuban al-^{c^aqrab} The claw of the scorpion :
- (19/δ Lib) 4.91 Zuben Elakribi or Mulu-lizi (see γ Lib) :
- (η Lib) 5.41 Zuben Hakrabi [Zuban Alakrab] (see γ Lib) :
- (21/ν Lib) (or Zuben Hakrabim, see γ Lib) 5.19 :
- (2/σ Lib) 3.29 Brachium or Cornu (or Zuben el Genubi, see α Lib; or Zuben Hakrabi, see γ Lib; or Ankaa, see α Phe) — eclipsing variable :Stars with Bayer designations: :: ε Lib 4.92; ζ Lib 5.53; θ Lib 4.13; ι Lib 4.54; κ Lib 4.75; λ Lib 5.04; μ Lib 5.32; ξ¹ Lib 5.78; ξ² Lib 5.48; ο Lib 6.14; τ Lib 3.66; υ Lib 3.60 :Stars with Flamsteed designations: :: 2 Lib 6.22; 4 Lib 5.70; 5 Lib 6.33; 11 Lib 4.93; 12 Lib 5.27; 16 Lib 4.47; 17 Lib 6.61; 18 Lib 5.88; 22 Lib 6.41; 23 Lib 6.47 – has a planet; 25 Lib 6.07; 26 Lib 6.18; 28 Lib 6.16; 30 Lib 6.46; 32 Lib 5.64; 33 Lib 6.69; 34 Lib 5.82; 36 Lib 5.13; 37 Lib 4.61; 41 Lib 5.36; 42 Lib 4.97; 47 Lib 5.95; 48 Lib 4.95; 49 Lib 5.47; 50 Lib 5.53 :Other notable stars: :HR 5568

External links

- [http://www.allthesky.com/constellations/libra/ The Deep Photographic Guide to the Constellations: Libra]
- [http://astrology.yahoo.com/astrology/general/dailyoverview/libra Libra Links on Yahoo.com]
- [http://www.astrology.com/ssc/libra.html?ice=ast,scopes,mssc Libra Links on Astrology.com]
- [http://www.doublesign.com/astro/western/signs.php?signid=libra Libra Links on DoubleSign.com] Category:Astrological signs ko:천칭자리 ja:てんびん座 th:กลุ่มดาวตาชั่ง

Virgo

See VIRGO (physics) for a French-Italian project in physics. ---- Virgo (20px, and Latin for virgin) is a constellation of the zodiac. Lying between Leo to the west and the Libra to the east, it is one of the largest constellations in the sky. It can be easily found through its bright α star, Spica.

Notable features

The most prominent star in Virgo is Spica (α Vir), which was sometimes considered to represent an ear of wheat in Virgo's hand. Spica makes it easy to locate Virgo, as it can be found by following the curve of the Big Dipper to Arcturus in Boötes and continuing from there in the same curve ("follow the arc to Arcturus and speed on to Spica"). Other bright stars in Virgo include β Vir (Zavijah), γ Vir (Porrima), δ Vir (Auva) and ε Vir (Vindemiatrix). Other fainter stars that were also given names are ζ Vir (Heze), η Vir (Zaniah), ι Vir (Syrma) and μ Vir (Rijl al Awwa). The star 70 Virginis is an extrasolar planetary system with one confirmed planet 6.6 times the mass of Jupiter. Due to the effects of precession, the First Point of Libra, (also known as the autumn equinox point) lies within the boundaries of Virgo. This is one of the two points in the sky where the celestial equator crosses the ecliptic (the other being the First Point of Aries, now in the constellation of Pisces.) This point will pass into the neighbouring constellation of Leo around the year 2440.

Notable deep sky objects

Because of the presence of a galaxy cluster (consequently called the Virgo cluster) within its borders 5° to 10° west of ε Vir (Vindemiatrix), this constellation is especially rich in galaxies. Some examples are M49 (elliptical), M58 (spiral), M59 (elliptical), M60 (elliptical), M61 (spiral), M84 (elliptical), M86 (elliptical), M87 (elliptical and a famous radiosource), M89 (elliptical) and M90 (spiral). A noted galaxy that is not part of the cluster is M104, a spiral galaxy also called the Sombrero Galaxy. It is located about 10° due west of Spica.

Mythology

Who exactly Virgo was considered to represent is uncertain; in history, it has been associated with nearly every prominent goddess, including Ishtar, Isis, Cybele, Mary, Mother of Jesus, and Athena. Virgo may also feature, along with Ursa Major, and Ursa Minor, as part of the source of the myth of Callisto, either as Callisto herself, or as Hera. Persephone (who in some mythologies, notably the Eleusinian Mysteries, was considered to be a form of Demeter) is often mentioned as well, Virgo being visible mainly in the spring months when she was believed to have risen from the underworld. According to one interpretation, the constellation depicts Astraea, the virgin daughter of the god Zeus and the goddess Themis. Astraea was known as the goddess of justice, and was identified as this constellation due to the presence of the scales of justice Libra nearby, and supposedly ruled the world at one point with her wise ways until mankind became so callous she returned to skies disgusted.

Astrology

The Western astrological sign Virgo of the tropical zodiac (August 23 - September 22) differs from the astronomical constellation and the Hindu astrological sign of the sidereal zodiac (September 16 - October 30). In some cosmologies, Virgo is associated with the classical element Earth, and thus called an Earth Sign (with Taurus and Capricorn). It is also one of the mutable signs (along with Gemini, Sagittarius, and Pisces). It is the domicile and exaltation of Mercury. Its polar opposite is Pisces. Each astrological sign is assigned a part of the body, viewed as the seat of its power. Virgo rules the intestines. The symbol for Virgo is the virgin or maiden.

Notable and named stars

Source: The Bright Star Catalogue, 5th Revised Ed., The Hipparcos Catalogue, ESA SP-1200

External links

- [http://www.allthesky.com/constellations/virgo/ The Deep Photographic Guide to the Constellations: Virgo]
- [http://astrology.yahoo.com/astrology/general/dailyoverview/virgo Virgo Links on Yahoo.com]
- [http://www.astrology.com/ssc/virgo.html?ice=ast,scopes,mssc Virgo Links on Astrology.com]
- [http://www.doublesign.com/astro/western/signs.php?signid=virgo Virgo Links on DoubleSign.com] Category:Astrological signs ko:처녀자리 ja:おとめ座 th:กลุ่มดาวหญิงสาว

Libra

Notable features

Mythology

Astrology

Stars

External links

Eight

8 (eight) is the natural number following 7 and preceding 9. The SI prefix for 1000⁸ is yotta (Y), and for its reciprocal yocto (y).

In mathematics

It is a composite number, its proper divisors being 1, 2, and 4. Eight is a power of two, being 2³, or two cubed. 8 is the base of the octal number system, which is mostly used with computers. In octal, one digit represents three bits. In modern computers, a byte is a grouping of eight bits, also called an octet. The number 8 is a Fibonacci number, being 3 plus 5. The next Fibonacci number is 13. 8 is also a Harshad number. In binary code eight is 1000; in ternary code eight is 22; in quaternary numeral system code eight is 20; in quinary eight is 13; in senary eight is 12; in septenary eight is 11; in octal eight is 10; in novenary code and all codes above (such as decimal and hexadecimal) eight is 8. In Roman numerals eight is VIII. A polygon with eight sides is an octagon. Figurate numbers representing octagons (including eight) are called octagonal numbers. A polyhedron with eight faces is an octahedron. Sphenic numbers always have exactly eight divisors. 8 is the dimension of the octonions and is the highest possible dimension of a normed division algebra.

The Arabic glyph

Image:Evo8glyph.png In the beginning, various groups in India wrote 8 more or less in one stroke as a curve that looks like an uppercase H with the bottom half of the left line and the upper half of the right line removed. At one point this glyph came close to looking like our modern 5. With the western Ghubar Arabs, the similarity of the glyph to 5 was banished by connecting the beginning and the end of stroke together, and it was only a matter of the Europeans rounding the glyph that led to our modern 8. In fonts with text figures, 8 usually has an ascender, for example, Image:TextFigs148.png.

In science

- The atomic number of oxygen
- In physics, the second magic number.
- In particle physics, the eightfold way is used to classify sub-atomic particles.

In astronomy

: Messier object M8, a magnitude 5.0 nebula in the constellation Sagittarius. : The New General Catalogue [http://www.ngcic.org/ object] NGC 8, a double star in the constellation Pegasus :The Saros [http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros1-175.html number] of the solar eclipse series which began on 2579 BCE March 7 and ended on 1281 BCE April 26. The duration of Saros series 8 was 1298.1 years, and it contained 73 solar eclipses. :The Saros [http://sunearth.gsfc.nasa.gov/eclipse/LEsaros/LEsaros1-175.html number] of the lunar eclipse series which began on 2512 BCE July 27 and ended on 961 BCE February 13. The duration of Saros series 7 was 1550.6 years, and it contained 87 lunar eclipses.

In music

- A note played for one-eighth the duration of a whole note is called an eighth note, or quaver.
- Songs with the number eight in their title include the Byrds's "Eight Miles High" and the Beatles's "Eight Days a Week".

In sports

- In chess, each side has eight pawns; see also Eight queens puzzle
- In rugby union the number eight central back row position wears the 8 shirt.
- In the Nextel Cup series, 8 is Dale Earnhardt Jr.'s car number.
- In baseball, eight represents the center fielder's position.
- Eight ball billiards is played with 15 balls; the black ball numbered 8 is the most important one. Magic 8 Ball is a randomized process of predicting the future or answering various questions, packaged to resemble this ball and often sold as a fortune-telling device.
- The retired numbers of former baseball players Yogi Berra, Willie Stargell, Carl Yastrzemski, Joe Morgan, and Cal Ripken, Jr.

In technology

- Many (mostly historic) computer architectures are eight-bit, among them the Nintendo Entertainment System.
- On most phones, the 8 key is associated with the letters T, U, and V, but on the BlackBerry it is the key for B and N.

In other fields

N
- Eight (八, formal writing 捌, pinyin bā) is considered a lucky number in Chinese culture because it sounds like the word "prosper" (發 pinyin fā).
- There are eight musicians in an octet.
- There are eighty-eight (88) keys on a piano.
- Eight babies delivered in one birth are called octuplets. The first set of eight surviving babies, the Louis-Chukwu Octuplets, were born in 1998.
- All spiders, and more generally all arachnids, have eight legs. An octopus has eight tentacles.
- Timothy Leary identified a hierarchy of eight levels of consciousness.
- The wheel of life has eight spokes.
- October was the eighth month in the Roman calendar; August is currently the eighth month.
- The Noble Eightfold Path in the Buddhist faith has eight steps.
- In Terry Pratchett's Discworld series, eight is a holy number and is considered taboo. Eight is not safe to be said by wizards on the Discworld and is the number of Bel-Shamharoth. Also, there are eight days in a Disc week and eight colours in a Disc spectrum, the eighth one being Octarine.
- Referring to the shape of the numeral, eight was represented in bingo slang, before political correctness, as 'One Fat Lady.' Eighty-eight was 'Two Fat Ladies'.
- "Eight maids a-milking" is the gift on the eighth day of Christmas in the "Twelve days of Christmas" carol.
- I-8 is the designation of the US interstate highway that runs from San Diego, California to Casa Grande, Arizona.
- Eight is the number of categories the VALS system uses to classify consumer groups, and the number of categories used by Fallon-McElligott's system for teen marketing.
- There is a brand of chocolates filled with peppermint-flavoured cream called "After Eight", referring to the time 8 p.m.
- There are eight vegetables in V8 juice.
- The ordinal adjective is octonary.
- In Astrology, Scorpio is the 8th astrological sign of the Zodiac.
- Using hyperbole, the Beatles sang about loving their addressee "Eight Days a Week". Also from music is the 8-track.
- The numeral "8" is sometimes used in writing to represent the syllable "ate", as in writing "H8" for "hate", or "congratul8ons" for "congratulations". Avril Lavigne's song "Sk8er Boi" uses this convention in the title. Often found in vanity plates.
- Several groups of "Eight Immortals"
- Eight Principles of Yong
- War of the Eight Princes
- The silver piece of eight was coined in the Spanish Empire and moved trade around the world.
- The symbol for infinity looks like a fallen eight.
- A figure 8 is the common name of a geometric shape, often used in the context of sports, such as skating.
- Lewis Carrolls poem The Hunting of the Snark has 8 "fits" (cantos), which is noted in the full name "The Hunting of the Snark - An Agony, in Eight Fits.
- "Section 8" is common U.S. slang for "crazy", based on the U.S. military's Section 8 discharge for mentally unfit personnel.
- A euphemism for masturbation within a small group of gamers who coined the expression (placing "masturbation" in the eighth space in a list of instructions, as a joke).
- 8 apparitions appear to Macbeth in Act 4 scene 1 of Shakespeare's Macbeth as representations of the 8 descendents of Banquo who will be king.
- Historical years: 8 A.D., 8 B.C., or 1908
- 8 is one of the "Lost Numbers" on the television show, Lost, along with 4, 15, 16, 23, and 42. 08 ko:8 ja:8 th:8

Roman calendar

The Roman calendar changed its form several times in the time between the foundation of Rome and the fall of the Roman Empire. This article generally discusses the early Roman or 'pre-Julian' calendars. The calendar used after 46 BC is discussed under the Julian calendar. Julian calendar and Sextilis, and allows for the insertion of an intercalary lunar month.]]

History of the Calendar

To begin with it was a lunar calendar containing ten months, starting at the vernal equinox, traditionally invented by Romulus, the founder of Rome about 753 BC. However it seems to have been based on the Greek lunar calendar. The months at this time were
- Martius (31 days)
- Aprilis (30 days)
- Maius (31 days)
- Junius (30 days)
- Quintilis (31 days)
- Sextilis (30 days)
- September (30 days)
- October (31 days)
- November (30 days) and
- December (30 days) Thus the calendar year lasted 304 days and there were about 61 days of winter that did not fall within the calendar. The first reform of the calendar was attributed to Numa Pompilius, the second of the seven traditional Kings of Rome. He is said to have reduced the 30-day months to 29 days and to have added January (29 days) and February (28 days) to the end of the calendar around 713 BC, and thus brought the length of the calendar year up to 355 days:
- Martius (31 days)
- Aprilis (29 days)
- Maius (31 days)
- Iunius (29 days)
- Quintilis (31 days)
- Sextilis (29 days)
- September (29 days)
- October (31 days)
- November (29 days)
- December (29 days)
- Ianuarius (29 days)
- Februarius (28 days) In order to keep the calendar year roughly aligned with the solar year, a leap month of 27 days, the Mensis Intercalaris, sometimes also known as Mercedonius or Mercedinus, was added from time to time at the end of February, which was shortened to 23 or 24 days. The resulting year was either 377 or 378 days long. The decision to insert the intercalary month, and its placement, was the responsibility of the pontifex maximus. On average, this happened roughly in alternate years. The system of aligning the year through intercalary months broke down at least twice. The first time was during and after the Second Punic War. It led to the reform of the Lex Acilia in 191 BC. The details of this reform are unclear, but it appears to have successfully regulated intercalation for over a century. The second breakdown was in the middle of the first century BC. This breakdown may have been related to the increasingly chaotic and adversarial nature of Roman politics at the time. The position of pontifex maximus was not a full-time job; it was held by a member of the Roman elite, who would almost invariably be involved in the machinations of Roman politics. Because a Roman calendar year defined the term of office of elected Roman magistrates, a pontifex maximus would have reason to lengthen a year in which he or his allies were in power, or to not lengthen a year in which his political opponents held office. It was only after Julius Caesar, who had been pontifex maximus for some years, seized absolute power that the calendar was overhauled, with the result being the Julian calendar.

Months

The Romans had special names for 3 specific days in each month. The system was originally based on phases of the Moon (Luna), and these days were probably declared when the lunar conditions were right. After the reforms of Numa Pompilius, they occurred on fixed days.
- Kalends - first day of the month, from which the word "calendar" is derived. Interest on debt was due on Kalends.
- Nones – depending on the month, could be the 5th or the 7th day; traditionally the day of the Half Moon
- Ides – depending on the month, could be the 13th or the 15th day; traditionally the day of the Full Moon :Months with Ides and Nones occurring on the 13th/5th day: January, February, April, June, August, September, November, December :Months with Ides and Nones occurring on the 15th/7th day: March, May, July, October -- :a mnemonic: ::In March, July, October, May ::The IDES fall on the fifteenth day; ::The NONES the seventh; but all besides ::Have two days less for Nones and Ides. Days were numbered in a way that is quite different from the modern Western calendar. The Romans did not count the days of the month retrospectively, looking back to the first of the month (that is: 1st, 2nd day since the start of the month, 3rd day since the start of the month). They counted forward to their named days. Also, to the distress of moderns trying to work out dates in Roman calendar documents, they counted inclusively, so that 2 September is considered 4 days before 5 September, rather than 3 days before.

The example of September

The following example spells out how days were named for the pre-Julian September, which had only 29 days. It shows the Roman form of the date, the translation, and how we would say it today. The Romans used abbreviations: "a.d." = "ante diem" = "day before", "prid." = "pridie" = "the day before", "Kal" = "Kalends" etc. :Kal. Sept. = Kalends of September = 1 September :a.d. IV Non. Sept. = 4 days before the Nones of September = 2 September :a.d. III Non. Sept. = 3 days before the Nones of September = 3 September :prid. Non. Sept. = the day before the Nones of September = 4 September :Non. Sept. = Nones of September = 5 September :a.d. VIII Id. Sept. = 8 days before the Ides of September = 6 September :a.d. VII Id. Sept. = 7 days before the Ides of September = 7 September and so on till :a.d. III Id. Sept. = 3 days before the Ides of September = 11 September :prid. Id. Sept. = the day before the Ides of September = 12 September :Id. Sept. = Ides of September = 13 September :a.d. XVII Kal. Oct. = 17 days before the Kalends of October = 14 September :a.d. XVI Kal. Oct. = 16 days before the Kalends of October = 15 September and so on till :a.d. III Kal. Oct. = 3 days before the Kalends of October = 28 September :prid. Kal. Oct. = the day before the Kalends of October = 29 September :Kal. Oct. = Kalends of October = 1 October Notice that by counting inclusively and by having a special name for the day before a named day the Roman calendar loses the possibility of saying: 2 days before a named day. Also, after the Ides, the date no longer mentions September, but is counting down towards October. When Julius Caesar added a day to September, he didn't add it to the end of the month. Rather, the new day that got added was the day after the Ides: :a.d. XVIII Kal. Oct. = 18 days before the Kalends of October = 14 September As a result, the position of all the following dates in September got bumped up by one day. This has some unexpected effects. For example, the emperor Augustus was born on 23 September 63 BC. In the pre-Julian calendar this is 8 days before the Kalends of October (or, in Roman style, a.d. VIII Kal. Oct.), but in the Julian calendar it is 9 days (a.d. IX Kal. Oct.). Because of this ambiguity, in some parts of the Empire his birthday was celebrated on both dates, i.e. (for us) on both 23 and 24 September.

Days of the week

The Roman Republic, like the Etruscans, used a "market week" of eight days, marked as A to H in the calendar. A market was held on the eighth day. For the Romans, who counted inclusively, this was every ninth day, hence the market became called "nundinae". Since the length of the year was not a multiple of 8 days, the letter for the market day (known as a "nundinal letter") changed every year. For example, if the current letter for market days was A and the year was 355 days long, then the letter for the next year would be F. The market cycle was a fundamental rhythm of daily life, and the market day was the day that country people would come to the city. For this reason, a law was passed in 287 BC (the Lex Hortensia) that forbade the holding of meetings of the comitia (for example to hold elections) on market days, but permitted the holding of legal actions. In the late republic, a superstition arose that it was unlucky to start the year with a market day (i.e. for the market day to fall on 1 January, with a letter A), and the pontiffs, who regulated the calendar, took steps to avoid it. Because the market cycle was absolutely fixed at 8 days under the Republic, information about the dates of market days is one of the most important tools we have for working out the Julian equivalent of a Roman date in the pre-Julian calendar. In the early Empire, the Roman market day was occasionally changed. The details of this are not clear, but one likely explanation is that it would be moved by one day if it fell on the same day as the festival of Regifugium, an event that could occur every other Julian leap year. When this happened the market day would be moved to the next day, which was the bissextile (leap) day. The modern seven-day week came into use during the early imperial period, after the Julian calendar came into effect, apparently stimulated by immigration from the Roman East. For a while it coexisted alongside the old 8-day nundinal cycle, and fasti are known which show both cycles. It was finally given official status by Constantine in 321. The days of the week were dedicated to the seven planets. They were (note the similarities of some of the days with French and Spanish and other Romance languages):
- Sunday – Dies Solis (day of the sun)
- Monday – Dies Lunae (day of the moon)
- Tuesday – Dies Martis (day of Mars)
- Wednesday – Dies Mercuri (day of Mercury)
- Thursday – Dies Iovis (day of Jupiter)
- Friday – Dies Veneris (day of Venus)
- Saturday – Dies Saturni (day of Saturn)

Character of the Day

An aspect of the Roman calendar that is quite unfamiliar to us is that each day had a "character", which was marked in the fasti. The most important of these were dies fasti, marked by an F, on which legal matters could normally be heard, dies nefasti, marked by an N, on which they could not, and dies comitiales, marked by a C, on which meetings of the public assemblies known as comitia were permitted, subject to other constraints such as the Lex Hortensia. A few days had a different character, e.g. EN (endotercissus or perhaps endoitio exitio nefas), a day in which legal actions were permitted on half of the day only, and NP, which were public holidays.

Years

In the Roman Republic, the years were not counted. Instead they were named after the consuls who were in power at the beginning of the year (see List of Republican Roman Consuls). For example, 205 BC was The year of the consulship of Publius Cornelius Scipio Africanus and Publius Licinius Crassus. However, in the later Republic, historians and scholars began to count years from the founding of the city of Rome. Different scholars used different dates for this event. The date most widely used today is that calculated by Varro, 753 BC, but other systems varied by up to several decades. Dates given by this method are numbered ab urbe condita (meaning after the founding of the city, and abbreviated AUC). When reading ancient works using AUC dates, care must be taken to determine the epoch used by the author before translating the date into a Julian year. The first day of the consular term, which was effectively the first day of the year, changed several times during Roman history. It became 1 January in 153 BC. Before then it was 15 March. Earlier changes are a little less certain. There is good reason to believe it was 1 May for most of the third century BC, till 222 BC. Livy mentions consulates starting on 1 July before then, and arguments exist for other dates at earlier times.

Converting Pre-Julian Dates

Finding the Julian equivalent of a Roman date can be quite tricky. Even early Julian dates, before the leap year cycle was stabilised, are not quite what they appear to be. For example, it is well known that Julius Caesar was assassinated on the Ides of March in 44 BC, and this is usually converted to 15 March 44 BC. While he was indeed assassinated on the 15th day of the Roman month Martius, the equivalent date on the modern Julian calendar is probably 14 March 44 BC. Finding the exact Julian equivalent of a pre-Julian date is much harder. Since we have an essentially complete list of the consuls, it is not difficult to find the Julian year that generally corresponds to a pre-Julian year. However, our sources very rarely tell us which years were regular, which were intercalary, and how long an intercalary year was. For this reason, pre-Julian dates can be very misleading. We do have a number of clues to help us. First, we know when the Julian calendar began, although there is some argument about it. We have detailed sources for the previous decade or so, mostly in the letters and speeches of Cicero. Combining these with what we know about how the calendar worked, especially the nundinal cycle, we can accurately convert Roman dates after 58 BC. Also, the histories of Livy give us exact Roman dates for two eclipses in 190 BC and 168 BC, and we have a few loose synchronisms to dates in other calendars which help to give rough (and sometimes exact) solutions for the intervening period. Before 190 BC the alignment between the Roman and Julian years is determined by clues such as the dates of harvests mentioned in the sources. This allows us to estimate approximate Julian equivalents of Roman dates back to the start of the First Punic War in 264 BC. However, the number of years before 45 BC for which we can accurately and precisely convert Roman dates to Julian dates is very small.

References

- Plutarch - Numa Pompilius
- Ovid - Fasti
- Bickerman, E.J. Chronology of the Ancient World. London: Thames & Hudson, 1969, rev. ed. 1980.
- Michels, A. K. The Calendar of the Roman Republic Princeton, 1967

External links

- [http://www.12x30.net/linked.html Bill Hollon's site]
- [http://webexhibits.org/calendars/calendar-roman.html Early Roman Calendar - History]
- [http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA
- /Calendarium.html Smith's Dictionary article]
- [http://www.tyndale.cam.ac.uk/Egypt/ptolemies/chron/roman/chron_rom_intro.htm Roman Dates (Chris Bennett's site)]
- [http://penelope.uchicago.edu/~grout/encyclopaedia_romana/calendar/romancalendar.html James Grout: The Roman Calendar, part of the Encyclopædia Romana]
- ja:ローマ暦

February

February is the