A common year is a calendar year with 365

day A day is the time rotation period, period of a full Earth's rotation, rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, ...

s, as distinguished from a ''

leap year A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) compared to a common year. The 366th day (or 13th month) is added to keep t ...

'', which has 366 days. More generally, a common year is one without intercalation. The

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...

, used by the majority of the world, employs both common years and leap years. This is to keep the calendar aligned with the

tropical year A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronom ...

, which does not contain an exact number of days. A common year is approximately a quarter day (six hours) shorter than a tropical year, which has 365.24 days. If the Gregorian calendar only used common years and omitted leap years, the calendar would be out of sync with the tropical year by approximately 24 days in 100 years. In the Gregorian calendar, 303 out of every 400 years are common years. Leap years are any years that are divisible by 4, unless it can also be divided by 100, in which case it is a common year. One exception is if the year can be divided by 4, 100, ''and'' 400 - these years are leap years. The extra common years are added to account for the fact that common years are 5 hours, 48 minutes, and 46 seconds shorter than a tropical year, rather than six hours exactly. By comparison, in the

Julian calendar The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts ...

, 300 out of every 400 years are common years, with every fourth year being a leap year without exception. The common year has 52

week A week is a unit of time equal to seven days. It is the standard time period used for short cycles of days in most parts of the world. The days are often used to indicate common work days and rest days, as well as days of worship. Weeks are ofte ...

s and one day, hence a common year always begins and ends on the same day of the week (for example, January 1 and December 31 both fall on a Wednesday in 2025) and the year following a common year will start on the subsequent day of the week. In common years, February has exactly four weeks, so March begins on the same day of the week as February does. November also begins on this day. For example, February 2025 began on a Saturday, thus March 2025 also began on a Saturday. November 1, 2025, will also start on a Saturday. Each common year has 179 even-numbered days and 186 odd-numbered days.

Calendars

* Common year starting on Monday *

Common year starting on Tuesday A common year starting on Tuesday is any non-leap year (i.e. a year with 365 days) that begins on Tuesday, 1 January, and ends on Tuesday, 31 December. Its dominical letter hence is F. The most recent year of such kind was 2019, and the next one wi ...

Common year starting on Wednesday A common year starting on Wednesday is any non-leap year (a year with 365 days) that begins on Wednesday, January 1, and ends on Wednesday, December 31. Its dominical letter hence is E. The current year, 2025, is a common year starting on Wedne ...

Common year starting on Thursday A common year starting on Thursday is any non-leap year (i.e. a year with 365 days) that begins on Thursday, 1 January, and ends on Thursday, 31 December. Its dominical letter hence is D. The most recent year of such kind was 2015, and the next ...

Common year starting on Friday A common year starting on Friday is any non-leap year (i.e. a year with 365 days) that begins on Friday, 1 January, and ends on Friday, 31 December. Its dominical letter hence is C. The most recent year of such kind was 2021, and the next one wil ...

Common year starting on Saturday A common year starting on Saturday is any non-leap year (i.e. a year with 365 days) that begins on Saturday, 1 January, and ends on Saturday, 31 December. Its dominical letter hence is B. The most recent year of such kind was 2022, and the next ...

Common year starting on Sunday A common year starting on Sunday is any non-leap year (i.e. a year with 365 days) that begins on Sunday, January 1, 1 January, and ends on Sunday, December 31, 31 December. Its dominical letter hence is A. The most recent year of such kind was 2023 ...

References

Calendars Types of year Units of time {{time-stub