Calendar Year

We explain what a calendar year is and how it differs from a calendar year. In addition, we tell you what a leap year is and much more.

calendar year
The calendar year has become a global convention in the contemporary era.

What is a calendar year?

one calendar year It is the name given to the standard period of twelve months that in the Western calendar represents a year. It covers, in strict order, the months of January, February, March, April, May, June, July, August, September, October, November and December, from January 1 to December 31.

However, this is what happens in the Western calendar (currently the Gregorian calendar) as different peoples may have different calendar systemsand in those cases a calendar year will always be the period established for the year according to each system.

The western calendar method dates from 1582 and it is the result of reforms made to the Julian calendar (named after its creator, the Roman Emperor Julius Caesar) by Pope Gregory XIII. This system has become a global convention in the contemporary era, although it coexists with calendars from different cultures, such as the Chinese or Muslim calendars.

The existence of different calendars (and therefore different ways of thinking about a calendar year) show that there are different ways of culturally organizing the passage of time.

One calendar year, in any event, spans 365 days in an ordinary year and 366 in a leap year (each 4 years). Although they are similar, a calendar year should not be confused with the astronomical year (expressed by the transit of the planet around the Sun) or with a natural year (365 calendar days, from one date to another 12 months later). The calendar year is taken as an established unit of time, closed in on itself, which begins and ends before being replaced by another similar one.

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See also: Year

Calendar year and calendar year

The difference between the calendar year and the calendar year has nothing to do with its length (twelve months) but with the way it is organized. A calendar year, as its name indicates, always obeys the order established in the calendars: it starts on January 1 and ends on December 31, and it is handled as a standard period of time that is repeated as the years go by.

Instead, A calendar year is a period of twelve months taken from any date, until its repetition the following year.. Thus, there is a calendar year between August 1, 2009 and August 1, 2010, since twelve months elapse between one date and the other.


It is known as a leap year a year endowed with an additional day during the month of February. This day arises from the accumulation of the remaining portions of time in the span of 365 days of the year, since in reality this figure is not exact, but rather more than 5 hours a year are left over. For that reason, leap years have 366 days (adding February 29) and occur every four years to offset the calendar system.

These years are called “leap” due to the Latin expression “bis sextus dies ante calendas martii” (“repeated on the sixth day before the first day of March”), popularly abbreviated to “bis sextus”, and it is because the Roman Julian calendar inserted the extra day between February 23 and 24. On the other hand, in the Gregorian calendar that has been used in the West since 1582, this extra day was moved to February 29.

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More in: Leap Year

business year and fiscal year

One fiscal year and one business year are two ways of organizing a calendar year according to the needs of an economic or bureaucratic sector of society. This means that although the companies use the same formal calendar, this is not necessarily the same as the formal calendar of activities of the fiscal and tax sector, or of the commercial and business sector.

  • Fiscal or financial year. It has a duration of 12 months, but it does not necessarily coincide with the calendar year, since it adjusts to the tax regulations and the closure of company activities (accounting closure), that is, to the State bureaucracy and administrative management.
  • business year. It has a duration of only 360 days, since it is designed based on a simplification of the calendar year, assigning an average of 30 days to each month in a conventional way. This business calendar is useful for organizing investments and for calculating bank interest and discounts.

School year and gap year

calendar school year
The school year is the period in which students regularly attend schools.

In the educational and academy field, the school year or school year is called the annual cycle of studies that is dictated in the schools, institutes and universities of a country.

During this time, students regularly attend their educational centers, so that vacation periods are not part of the school year. For example, in some countries the school year starts in September and ends in July (in the northern hemisphere), while in others it starts in March and ends in November (in the southern hemisphere).

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Instead, The sabbatical year is called, in the same context, the year of rest or preparation that teachers and university professors can take, from time to time, and thus get away from the teaching routine and acquire new knowledge. The latter can be done in the same country or as a guest in foreign university programs.

The name of the sabbatical year comes from the Hebrew shabbat (translatable as “day of rest”), sharing origin with the name of the day Saturday. In ancient times, this was the name given to the agricultural custom of letting the soil rest for a year after six consecutive harvests, in order to preserve its nutrients and moisture.


In astrophysics, a “light year” (sometimes abbreviated to al. or al) is called a measure of length equal to the distance a beam of light travels in a vacuum during a consecutive Julian year (ie, for 365.25 days of 24 hours each). This means that one light year is equal to 9.46 x 1012 kilometresthat is, 9,460,730,472,580.8 kilometers.

With this unit it is possible to express simply and efficiently the immense distances of outer space, since using kilometers would make the figures too long and cumbersome.

The light year was formally used for the first time in an astronomical popularization article published in 1851 by the German Otto Ule (1820-1876), and from the beginning it drew attention to the fact that it contained the temporal term “year”, for which reason it was questioned. the convenience of its use, very popular at present. However, different specialists in the field prefer the use of the unit parsec.

Continue with: Seasons of the year


  • “Leap Year” on Wikipedia.
  • “Calendar year” on Wikipedia.
  • “Business Year” on Wikipedia.