Calendar

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.

2025 in other calendars

Gregorian calendar	2025 MMXXV
Ab urbe condita	2778
Armenian calendar	1474 ԹՎ ՌՆՀԴ
Assyrian calendar	6775
Bahá'í calendar	181–182
Balinese saka calendar	1946–1947
Bengali calendar	1432
Berber calendar	2975
British Regnal year	3 Cha. 3 – 4 Cha. 3
Buddhist calendar	2569
Burmese calendar	1387
Byzantine calendar	7533–7534
Chinese calendar	甲辰年 (Wood Dragon) 4721 or 4661     — to — 乙巳年 (Wood Snake) 4722 or 4662
Coptic calendar	1741–1742
Discordian calendar	3191
Ethiopian calendar	2017–2018
Hebrew calendar	5785–5786
Hindu calendars
- Vikram Samvat	2081–2082
- Shaka Samvat	1946–1947
- Kali Yuga	5125–5126
Holocene calendar	12025
Igbo calendar	1025–1026
Iranian calendar	1403–1404
Islamic calendar	1446–1447
Japanese calendar	Reiwa 7 (令和７年)
Javanese calendar	1958–1959
Juche calendar	114
Julian calendar	Gregorian minus 13 days
Korean calendar	4358
Minguo calendar	ROC 114 民國114年
Nanakshahi calendar	557
Thai solar calendar	2568
Tibetan calendar	阳木龙年 (male Wood-Dragon) 2151 or 1770 or 998     — to — 阴木蛇年 (female Wood-Snake) 2152 or 1771 or 999
Unix time	1735689600 – 1767225599

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

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.

Related pages

• Anno Domini (AD)
• Christian calendar
• Common Era (CE)
• Friday (Muslim)
• Saturday (Jewish)
• Sunday (Christian)
• Gregorian calendar (Christian)
• Hebrew calendar (Jewish)
• Islamic calendar (Muslim)

Other websites

• Calendar for many years, for many countries
• Calendar -Citizendium