What is "common year"

Year \Year\, n. [OE. yer, yeer, [yogh]er, AS. ge['a]r; akin to OFries. i?r, g?r, D. jaar, OHG. j[=a]r, G. jahr, Icel. [=a]r, Dan. aar, Sw. [*a]r, Goth. j?r, Gr. ? a season of the year, springtime, a part of the day, an hour, ? a year, Zend y[=a]re year. [root]4, 279. Cf. Hour, Yore.]

1. The time of the apparent revolution of the sun trough the ecliptic; the period occupied by the earth in making its revolution around the sun, called the astronomical year; also, a period more or less nearly agreeing with this, adopted by various nations as a measure of time, and called the civil year; as, the common lunar year of 354 days, still in use among the Mohammedans; the year of 360 days, etc. In common usage, the year consists of 365 days, and every fourth year (called bissextile, or leap year) of 366 days, a day being added to February on that year, on account of the excess above 365 days (see Bissextile).

   Of twenty year of age he was, I guess.
   --Chaucer.

   Note: The civil, or legal, year, in England, formerly commenced on the 25th of March. This practice continued throughout the British dominions till the year 175

2. 2. The time in which any planet completes a revolution about the sun; as, the year of Jupiter or of Saturn.

3. pl. Age, or old age; as, a man in years.
   --Shak.

   Anomalistic year, the time of the earth's revolution from perihelion to perihelion again, which is 365 days, 6 hours, 13 minutes, and 48 seconds.

   A year's mind (Eccl.), a commemoration of a deceased person, as by a Mass, a year after his death. Cf. A month's mind, under Month.

   Bissextile year. See Bissextile.

   Canicular year. See under Canicular.

   Civil year, the year adopted by any nation for the computation of time.

   Common lunar year, the period of 12 lunar months, or 354 days.

   Common year, each year of 365 days, as distinguished from leap year.

   Embolismic year, or Intercalary lunar year, the period of 13 lunar months, or 384 days.

   Fiscal year (Com.), the year by which accounts are reckoned, or the year between one annual time of settlement, or balancing of accounts, and another.

   Great year. See Platonic year, under Platonic.

   Gregorian year, Julian year. See under Gregorian, and Julian.

   Leap year. See Leap year, in the Vocabulary.

   Lunar astronomical year, the period of 12 lunar synodical months, or 354 days, 8 hours, 48 minutes, 36 seconds.

   Lunisolar year. See under Lunisolar.

   Periodical year. See Anomalistic year, above.

   Platonic year, Sabbatical year. See under Platonic, and Sabbatical.

   Sidereal year, the time in which the sun, departing from any fixed star, returns to the same. This is 365 days, 6 hours, 9 minutes, and 9.3 seconds.

   Tropical year. See under Tropical.

   Year and a day (O. Eng. Law), a time to be allowed for an act or an event, in order that an entire year might be secured beyond all question.
   --Abbott.

   Year of grace, any year of the Christian era; Anno Domini; A. D. or a. d.

n. A year that is not a leap year. A 365-day year.

n. a year that is not a leap year [syn: 365 days]

A Common year is a calendar year with exactly 365 days, in contrast to the longer leap year. More generally, a common year is one without intercalation. The Gregorian calendar (like the earlier Julian calendar) employs both common years and leap years to adjust for differing astronomical measurements of the year: sidereal and tropical.

The common year of 365 days has exactly 52 weeks and one day, hence a common year always begins and ends on the same day of the week. (For example: both January 1 and December 31 fell on a Friday in 2010). In a common year, February has exactly four weeks, so that month and March always start consecutively on the same day of the week.

In the Gregorian calendar, 303 of every 400 years are common years. By comparison, in the Julian calendar, 300 out of every 400 years are common years.

In the Lunisolar calendar and the Lunar calendar, a common year consists of 354 days.

The Common Year (CY) Reckoning is a fictional dating system used in the World of Greyhawk campaign setting for the Dungeons & Dragons role-playing game.

In the mid-1970s, Gary Gygax created a campaign world called Greyhawk for the new fantasy roleplaying game called Dungeons and Dragons that he was helping to develop. In the 1980 TSR publication World of Greyhawk (TSR 9025), he included a brief timeline of twenty-one historical events that described a thousand years of history in order to explain how his world—the Flanaess—had arrived at its present state of affairs. There were five major cultures involved in this timeline, each of them with their own calendar system:

• Suloise: Suloise Dating or Suloise Dominion (SD)
• Olven: Olven Calendar (OC)
• Bakluni: Baklunish Hegira or Baklunish Hierarchy (BH)
• Flan: Flan Tally (FT)
• Oeridian: Oeridian Record or Oeridian Reckoning (OR)

One of the major events of Gygax's timeline was an invasion by the Oeridian people, which forced other cultures to the peripheries of this land and led to the formation of the Great Kingdom of Aerdy. The first emperor marked the start of this new empire with a new universal calendar, Common Year Reckoning.

Gygax calculated all events that had taken place before 1 CY as negative numbers, and since there was no 0 CY—the year previous to 1 CY was -1 CY—this forced an extra calculation when attempting to convert Common Year dates prior to 1 CY to the other calendar systems. However, by the start of Gygax's campaign (set as 576 CY), the Common Year Reckoning was used almost universally by most cultures, making conversions to the other calendar systems by dungeon masters largely unnecessary.

Days, weeks, and months within the Common Year are reckoned using the Greyhawk Calendar.