Calendar year

Today (at UTC+00)
Tuesday, 2 June 2026
Other calendars Armenian 17 Margach 1475 Bengali 19 Joishtho, BS 1433 Chinese Yin Fire Goat・Tail Mansion 17 Sìyue, Bǐngwǔnián (Xiaoman, 3 days until Mangzhong) Common Era 2 June 2026 CE Coptic 25 Pashons, AM 1742 Egyptian 17 Phaophi, NE 2775 Ethiopian 25 Genbot, AD 2018 French Republican Décade II, Quartidi de Prairial de l'Année 234 de la République Gregorian 2 June, AD 2026 Hebrew 17 Sivan, AM 5786 Islamic 16 Dhu al-Hijjah, AH 1447 (tabular method) ISO week date 2026-W23-2 Japanese 17 Uzuki, Reiwa 8 (Shōman, 4 days until Bōshu) Julian 20 May, AD 2026 (AM 7534) Julian day 2461194 Maya 13.0.13.11.11 4 Zotz, 1 Chuen Roman ante diem XIII Kalendas Iunias, AUC 2779 Solar Hijri 12 Khordad, SH 1405
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A calendar year begins on the New Year's Day of the given calendar system and ends on the day before the following New Year's Day, and thus consists of a whole number of days. The astronomer's mean tropical year, which is averaged over equinoxes and solstices, is currently 365.24219 days. As this is not an integer, solar calendars have strategies to adjust for the 0.24219 remainder. Neither is it a whole number of lunar months (being about 10 or 11 days more than 12 lunations) so lunisolar calendars also must include adjustments to resynchronise with the seasons. Pure lunar calendars ignore the solar cycle and instead have an invariant year of twelve lunar months that drifts through the seasons.

The Gregorian calendar year, which is in use as civil calendar in most of the world, begins on January 1 and ends on December 31. It has a length of 365 days in an ordinary year but, in order to reconcile the calendar year with the astronomical cycle, it has 366 days in a leap year. With 97 leap years every 400 years, the Gregorian calendar year has an average length of 365.2425 days.

Other formula-based calendars can have lengths which are further out of step with the solar cycle: for example, the Julian calendar (a solar calendar) has an average length of 365.25 days; the Hebrew calendar (a lunisolar calendar) has an average length of 365.2468 days. The Lunar Hijri calendar ("Islamic calendar") is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days.

A year can also be measured by starting on any other named day of the calendar, and ending on the day before this named day in the following year. This may be termed a "year's time", but is not a calendar year.

Parts

Quarter year

The calendar year can be divided into four quarters, often abbreviated as Q1, Q2, Q3, and Q4. Since they are three months each, they are also called trimesters. In the Gregorian calendar:

• First quarter, Q1: January 1 – March 31 (90 days or 91 days in leap years)
• Second quarter, Q2: April 1 – June 30 (91 days)
• Third quarter, Q3: July 1 – September 30 (92 days)
• Fourth quarter, Q4: October 1 – December 31 (92 days)

In some domains, weeks are preferred over months for scheduling and reporting, so they use quarters of exactly 13 weeks each, often following ISO week date conventions. One in five to six years has a 53rd week which is usually appended to the last quarter. It is then 98 days instead of 91 days long, which complicates comparisons.

In the Chinese calendar, the quarters are traditionally associated with the 4 seasons of the year:

• Spring: 1st to 3rd month
• Summer: 4th to 6th month
• Autumn: 7th to 9th month
• Winter: 10th to 12th month

Quadrimester

The calendar year can also be divided into three quadrimesters (from French quadrimestre), lasting for four months each. They can also be called the early, middle, or late parts of the year. In the Gregorian calendar:

• First quadrimester, early year: January 1 – April 30 (119 days or 120 days in leap years)
• Second quadrimester, mid-year: May 1 – August 31 (122 days)
• Third quadrimester, late year: September 1 – December 31 (121 days)

Semester

The calendar year can also be divided into two semesters, lasting six months each and often being abbreviated as S1 and S2. In the Gregorian calendar:

• First semester, S1: January 1 – June 30 (181 days or 182 days in leap years)
• Second semester, S2: July 1 – December 31 (184 days)

See also

• Academic term – Subdivision of the academic year at educational institutions
• Bissextus – Leap day (24 February used for two days) (historical usage)
• Calendar reform – Significant revision of a calendar system
• Common year – Calendar year with 365 days
• Fiscal year – One-year term for government and business financial reporting
• Intercalation (timekeeping) – Insertion of a leap day, week, or month
• ISO 8601 – International standards for dates and times
• ISO week date – Leap week calendar system
• Julian date – Days since the beginning of the Julian PeriodPages displaying short descriptions of redirect targets
• Julian year (astronomy) – a time interval of exactly 365.25 Earth days
• Julian year (calendar) – a year in the Julian calendar that is either 365 or 366 days, or 365.25 days on average
• Leap year – Calendar year with a day (or month) added
• Model year – Production date of a commercial product
• Ordinal date – Date written as number of days since first day of year
• Seasonal year – Time between successive recurrences of a seasonal event