Calendar

Kalender Indonesia

Calendar (part of a set) MET DP-13486-011

Equinozio da Pizzo Vento,tramonto fondachelli fantina, sicilia

Universal Calendar including a meton cycle

Sun and Moon Nuremberg chronicle

Calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. A date is the designation of a single, specific day within such a system. A calendar is also a physical record (often paper) of such a system. A calendar can also mean a list of planned events, such as a court calendar or a partly or fully chronological list of documents, such as a calendar of wills.

Types of Calendars

Calendars fall into several types, based on their use and the nature of their timekeeping. The most common distinction is between solar calendars, which are synchronized to the movement of the Sun, and lunar calendars, which are based on the phases of the Moon. A lunisolar calendar combines elements of both the lunar and solar calendars, to ensure that the lunar part of the calendar would not drift away from the season marked by the solar year.

Solar Calendars

A solar calendar is based on the Earth's rotation around the Sun. The Gregorian calendar, currently used by most of the world, is a solar calendar. It has 365 days in a common year and 366 days in a leap year, with a leap year occurring every 4 years to add a day to February to compensate for the fact that a solar year (the time it takes for Earth to orbit the Sun) is slightly more than 365 days.

Lunar Calendars

A lunar calendar is based on the cycle of the Moon's phases. The Islamic calendar or Hijri calendar is an example of a purely lunar calendar, where months correspond to the lunar cycle and therefore move through the seasons each year.

Lunisolar Calendars

The Hebrew calendar and the Chinese calendar are examples of lunisolar calendars. They adjust the lunar months to align with the solar year through the addition of an extra month every few years, thus maintaining the alignment with the seasons.

History

The development of calendars has been connected to the human need to organize activities and identify periods of time. Early calendars were often based on observable astronomical phenomena, such as the first sighting of the new Moon. The oldest known calendar is the Bronze Age lunar calendar found at Warren Field in Scotland, dating from around 8000 BC.

Calendar Systems

Different cultures have developed their own calendar systems, reflecting their particular needs, beliefs, and values. Besides the widely used Gregorian calendar, there are numerous other systems, including the Islamic calendar, the Hebrew calendar, the Hindu calendar, and the Mayan calendar, each with its own unique features and method of timekeeping.

Modern Use

Today, the Gregorian calendar is the internationally accepted civil calendar. However, many countries and cultures also use their traditional calendars alongside the Gregorian calendar for religious and cultural purposes.