Calendar

system of organizing days for social, religious, commercial, or administrative purposes
(Redirected from Calendars)

A calendar is a tool for organizing days. People use calendars to say when something happened, and for planning things that have not happened yet. The calendar gives the days names and numbers, called calendar dates. The dates are usually made based on how things in the sky seem to move. The year and month are based on motions of the Sun and moon. By knowing what day something happened or will happen, people have an easier life. Since the beginning of history, knowing when the seasons would start for crops was very important for farmers and people who eat.

2021 in various calendars
Gregorian calendar2021
MMXXI
Ab urbe condita2774
Armenian calendar1470
ԹՎ ՌՆՀ
Assyrian calendar6771
Bahá'í calendar177–178
Balinese saka calendar1942–1943
Bengali calendar1428
Berber calendar2971
British Regnal year69 Eliz. 2 – 70 Eliz. 2
Buddhist calendar2565
Burmese calendar1383
Byzantine calendar7529–7530
Chinese calendar庚子(Metal Rat)
4717 or 4657
    — to —
辛丑年 (Metal Ox)
4718 or 4658
Coptic calendar1737–1738
Discordian calendar3187
Ethiopian calendar2013–2014
Hebrew calendar5781–5782
Hindu calendars
 - Vikram Samvat2077–2078
 - Shaka Samvat1942–1943
 - Kali Yuga5121–5122
Holocene calendar12021
Igbo calendar1021–1022
Iranian calendar1399–1400
Islamic calendar1442–1443
Japanese calendarReiwa 3
(令和3年)
Javanese calendar1954–1955
Juche calendar110
Julian calendarGregorian minus 13 days
Korean calendar4354
Minguo calendarROC 110
民國110年
Nanakshahi calendar553
Thai solar calendar2564
Tibetan calendar阳金鼠年
(male Iron-Rat)
2147 or 1766 or 994
    — to —
阴金牛年
(female Iron-Ox)
2148 or 1767 or 995
Unix time1609459200 – 1640995199

Calendar systems have a beginning time or era. The calendar era is often a religion-based event, such as the birth of Jesus, but it may be a political event such as a coronation or the founding of a state. Dates that are counted from the coronation are called "regnal".

The three principal calendars most used today are the Gregorian, Hebrew, and Islamic calendars. Other calendar systems from many different parts of the world are also used.

BasisEdit

Calendars are based on three natural things:

  1. The Earth turns all the way around its axis.
  2. The Moon goes all the way around the Earth.
  3. The Earth goes all the way around the Sun.

The Earth turns all the way around its axis about 24 hours. It is called the Solar Day. Days of most calendars are strongly based on the Solar Day.

The Moon turns all the way around the Earth about 29 days, 12 hours, 44 minutes and 2 seconds. Months of some calendars are still strongly based on the Moon. These are called Lunar calendars, which lasts about 354-355 days. Solar calendars ignore the moon, and depend entirely on the Sun.

The Earth goes all the way around the Sun in about 365 days, 5 hours, 48 minutes and 46 seconds. This is called the Tropical Year. Years of most calendars are strongly based on the Tropical Year.

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