Calendar

system of organizing days for social, religious, commercial, or administrative purposes

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.

2024 in other calendars
Gregorian calendar2024
MMXXIV
Ab urbe condita2777
Armenian calendar1473
ԹՎ ՌՆՀԳ
Assyrian calendar6774
Bahá'í calendar180–181
Balinese saka calendar1945–1946
Bengali calendar1431
Berber calendar2974
British Regnal yearCha. 3 – 3 Cha. 3
Buddhist calendar2568
Burmese calendar1386
Byzantine calendar7532–7533
Chinese calendar癸卯(Water Rabbit)
4720 or 4660
    — to —
甲辰年 (Wood Dragon)
4721 or 4661
Coptic calendar1740–1741
Discordian calendar3190
Ethiopian calendar2016–2017
Hebrew calendar5784–5785
Hindu calendars
 - Vikram Samvat2080–2081
 - Shaka Samvat1945–1946
 - Kali Yuga5124–5125
Holocene calendar12024
Igbo calendar1024–1025
Iranian calendar1402–1403
Islamic calendar1445–1446
Japanese calendarReiwa 6
(令和6年)
Javanese calendar1957–1958
Juche calendar113
Julian calendarGregorian minus 13 days
Korean calendar4357
Minguo calendarROC 113
民國113年
Nanakshahi calendar556
Thai solar calendar2567
Tibetan calendar阴水兔年
(female Water-Rabbit)
2150 or 1769 or 997
    — to —
阳木龙年
(male Wood-Dragon)
2151 or 1770 or 998
Unix time1704067200 – 1735689599

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.

Basis change

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 Solar year. Years of most calendars are strongly based on the Solar year.

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