A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a physical record 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.
The Hijri calendar, or Arabic calendar also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual fasting and the annual season for the great pilgrimage. In almost all countries where the predominant religion is Islam, the civil calendar is the Gregorian calendar, with Syriac month-names used in the Levant and Mesopotamia but the religious calendar is the Hijri one.
Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months.
The Iranian calendars or Iranian chronology are a succession of calendars created and used for over two millennia in Iran, also known as Persia. One of the longest chronological records in human history, the Iranian calendar has been modified many times for administrative, climatic, and religious purposes. The most influential person in laying the frameworks for the calendar and its precision was the 11th century Persian polymath, Omar Khayyam. The modern Iranian calendar is currently the official civil calendar in Iran.
Thout, also known as Thoth and Tut, is the first month of the ancient Egyptian and Coptic calendars. It lies between 11 September and 10 October of the Gregorian calendar. The month of Thout is also the first month of the Season of Akhet (Inundation) in Ancient Egypt, when the Nile floods historically covered the land of Egypt; it has not done so since the construction of the High Dam at Aswan.
The intercalary month or epagomenal days of the ancient Egyptian, Coptic, and Ethiopian calendars are a period of five days in common years and six days in leap years in addition to those calendars' 12 standard months, sometimes reckoned as their thirteenth month. They originated as a periodic measure to ensure that the heliacal rising of Sirius would occur in the 12th month of the Egyptian lunar calendar but became a regular feature of the civil calendar and its descendants. Coptic and Ethiopian leap days occur in the year preceding Julian and Gregorian leap years.
There are two main holidays in Islam that are celebrated by Muslims worldwide: Eid al-Fitr and Eid al-Adha. The timing of both holidays are set by the lunar Islamic calendar, which is based upon the cycle of the moon, and so is different from the more common, European, solar-based Gregorian calendar. Every year, the Gregorian dates of the Islamic holidays change.
The Islamic New Year, also called the Hijri New Year, is the day that marks the beginning of a new lunar Hijri year, and is the day on which the year count is incremented. The first day of the Islamic year is observed by most Muslims on the first day of the month of Muharram. The epoch of the Islamic era was set as the year of the emigration of Muhammad and his followers from Mecca to Medina, known as the Hijrah, which equates to 622 CE in the Gregorian calendar. All religious duties, such as prayer, fasting in the month of Ramadan, and pilgrimage, and the dates of significant events, such as celebration of holy nights and festivals, are calculated according to the Islamic calendar.
The Hijri year or era is the era used in the Islamic lunar calendar. It begins its count from the Islamic New Year in which Muhammad and his followers migrated from Mecca to Yathrib in 622 CE. This event, known as the Hijrah, is commemorated in Islam for its role in the founding of the first Muslim community (ummah).
The Javanese calendar is the calendar of the Javanese people. It is used concurrently with two other calendars, the Gregorian calendar and the Islamic calendar. The Gregorian calendar is the official calendar of the Republic of Indonesia and civil society, while the Islamic calendar is used by Muslims and the Indonesian government for religious worship and deciding relevant Islamic holidays.
The Berber calendar is the agricultural calendar traditionally used by Berbers. The calendar is utilized to regulate the seasonal agricultural works.
The Arabic names of the months of the Gregorian calendar are usually phonetic Arabic pronunciations of the corresponding month names used in European languages. An exception is the Syriac calendar used in Iraq and the Levant, whose month names are inherited via Classical Arabic from the Babylonian and Hebrew lunisolar calendars and correspond to roughly the same time of year.
The Rumi calendar, a specific calendar based on the Julian calendar, was officially used by the Ottoman Empire after Tanzimat (1839) and by its successor, the Republic of Turkey until 1926. It was adopted for civic matters and is a solar based calendar, assigning a date to each solar day.
Fasli calendar or Fasli era is a harvest-based calendar system that was used across South Asia, but today is mainly used in Deccan. It was the official calendar of Hyderabad Deccan.
The Solar Hijri calendar is the official calendar of Iran. It is a solar calendar and is the one Iranian calendar that is the most similar to the Gregorian calendar, being based on the Earth's orbit around the Sun. It begins on the March equinox as determined by the astronomical calculation for the Iran Standard Time meridian and has years of 365 or 366 days. It is sometimes also called the Shamsi calendar and Khorshidi calendar. It is abbreviated as SH, HS or, sometimes as AHSh, while the lunar based Islamic calendar is usually abbreviated as AH.
The month names in Turkish are derived from three languages: either from Latin, Levantine Arabic, or from a native Turkish word. The Arabic-Aramaic month names themselves originate in the ancient Babylonian calendar, and are therefore cognate with the names of months in the Hebrew calendar, specifically Shevat, Nisan, Tammuz and Elul. The original Babylonian months were actual lunar months, as the Hebrew months of the same names are to this day, much like months in the Islamic calendar. Turkey has used Gregorian AD year numbering officially since 1926, though Gregorian calendar dates were in use since March 1917. The names of the months from February to September had been used in the now abandoned Rumi calendar, with the other four still retaining their old Arabic/Aramaic names. In 1945, four of them received names of Turkish origin by law number 4696 passed January 10, 1945.
In Bahrain, both the Gregorian and Islamic calendars are used in government transactions. Short dates are written in "Day/month/year" from; when writing in Arabic and English:
Several calendars have been used in pre-Islamic Arabia. Inscriptions of the ancient South Arabian calendars reveal the use of a number of local calendars, as do Safaitic inscriptions from the Harran desert in Syria and Jordan. At least some of the South Arabian calendars followed the lunisolar system, while the Safaitic calendar had fixed months and seasons and, very importantly, a seasonal star calendar strongly connected to the Zodiac and the position of the ʔanwāʔ. The ʔanwāʔ, a series of asterisms on or near the zodiac belt were the most important element in pre-Islamic astronomy. These stars were connected to the season, and they were used to forecast various phenomena such as rain, temperature, wind. Before the rise of Islam, diviners invoked these stars in rainmaking rituals called istisqāʔ. Rituals took place during specific times, when the sun was in one or the other of these ʔanwāʔ, some Safaitic texts speak of ritual cleansing while the sun is in Virgo (ngm) or Sagittarius (ṯbr); another text mentions a libation during the full moon of Gemini (gml). It is thus obvious that Zodiac constellations, the position of stars and the mansion of the Sun were very important criteria and had an important impact on the pre-Islamic Arabian calendar and ritual life.
The adoption of the Gregorian Calendar was an event in the early modern history of most cultures and societies, marking a change from their traditional dating system to the modern dating system – the Gregorian calendar – that is widely used around the world today. Some states adopted the new calendar from 1582, some did not do so before the early twentieth century, and others did so at various dates between. A few still have not, but except for these, the Gregorian calendar is now the world's civil calendar universally, although in many places an old style calendar remains used in religious or traditional contexts. During – and for some time after – the change between systems, it has been common to use the terms "Old Style" and "New Style" when giving dates, to indicate which calendar was used to reckon them.