A new moon and an Islamic month are born.
The Hijri calendar should not be confused with the Solar Hijri calendar used in Iran and Afghanistan.
tied to the phases of the moon
The Islamic calendar is a lunar calendar whose calculation of time is linked to the phases of the moon. each month lasts for a full lunation, which is the time between one new moon and the next. this lunar cycle encompasses all phases of the moon.
The timing of the months in the Islamic calendar is based on astronomical observation. a new month can only begin after a crescent moon is observed shortly after sunset. the waxing moon is the lunar phase that begins just after the new moon.
separate from the solar year
Unlike other calendar systems that use leap days or leap months to synchronize the calendar with the solar year, the Islamic calendar is completely separate from the astronomical seasons, which are marked by the equinoxes and solstices. an Islamic year always falls about 11 days less than the solar year.
For that reason, the Islamic calendar cannot be used for agriculture or other activities traditionally linked to the seasons, and most Muslim countries officially use the Gregorian calendar as their civil calendar along with the hijri system.
How accurate are the different calendar systems?
difficult to predict
The traditional version of the Islamic calendar requires that an authorized person or committee make an actual observation of the waxing moon to determine the length of each month.
This reliance on astronomical observations makes it difficult to predict the length of Islamic months. clouds and other adverse atmospheric conditions can obscure an otherwise visible crescent moon. when this happens, the month can be extended by a day, delaying both the start of the new month and the events associated with it. that is why the dates of Muslim holidays can change at short notice.
modified modern versions
Some Muslim countries and communities now use modified versions of the traditional calendar that are designed to make Islamic months and celebrations easier to predict.
A new month can also start on different days in different countries. because the time of moonset in a place depends on its longitude, a new month and key religious rituals, such as the fast of Ramadan, may begin a day earlier, for example in Muslim countries in West Africa than in indonesia or malaysia.
months in the Islamic calendar
The Islamic calendar has 12 months with 29 or 30 days. if the crescent moon is visible shortly after sunset on the evening of the 29th, the next day is the first day of the new month. if no sightings are made, a 30th day is added to the current month, followed by the first day of the next month.
the months of rajab, dhū al-qa‘dah, dhu al-Ḥijjah and muḥarram are considered holy.
when was year 1?
Like the Persian calendar, the Islamic reckoning of time begins in the year 622 AD. when the muslim prophet muhammad emigrated to medina. this event is known as hegira or hijrah, which explains the name hijri calendar.
In parallel with the letters ad (anno domini) used in the Christian calendar, years in the Islamic calendar are designated as h for hijrah or ah, meaning the Latin term anno hegirae.
Otherwise, the Persian and Islamic calendar systems are not related. the former is a solar calendar, so its year count differs substantially from that of the Islamic lunar calendar. For example, January 1, 2022 fell in the year 1443 Ah in the Hijri lunar calendar, which corresponds to the year 1400 in the Hijri solar calendar.
leap year rules
The year of the Islamic calendar is not designed to coincide with the length of a solar year, so it does not have a correction mechanism like leap days in the Gregorian calendar to compensate for the deviation. For each year that passes, Islamic dates fall on earlier dates in the Gregorian calendar. it takes 33 years until the hijri year has passed through a full Gregorian year and a given Islamic date falls on the same Gregorian date again.
Because Islamic calendar years are shorter than Gregorian years and the actual year number is lower, both calendar systems will display the same year number on a day. however, this will take some time: the year numbers will match on May 1, 20874 ce/ah.
To make Islamic time reckoning more predictable and universal, Muslim scholars developed the tabular Islamic calendar in the 8th century AD. this system uses arithmetic rules to determine the length of each month and inserts leap days periodically.
read more about the tabular islamic calendar
history and background
The modern hijri calendar is based on, and uses, the same month names as the pre-Islamic calendar used by the ancient Arabs. according to some sources, it was a lunisolar calendar in which the length of the months followed the phases of the moon and a leap month (nasī’) was regularly inserted to realign the reckoning of time with the solar year. After the Muslim conquest of Mecca, the leap month was abolished to create a purely lunar calendar.
Iranian astronomer al-Biruni (973 – 1048 AD) claims that Caliph Umar (c. 583 – 644 AD) introduced the Islamic year count in 638 AD. c. pre-Islamic time reckoning did not use year numbers, as each year was identified by an important event that occurred in it.
common years in the Gregorian calendar
leap years in the Gregorian calendar