Islamic calendar

The Hijri calendar, also known as the Islamic calendar, is a special way of counting years and months used by many people who follow Islam. It is a lunar calendar, which means it is based on the phases of the moon. This calendar has 12 months and usually has either 354 or 355 days in a year.

This calendar helps decide important Islamic holidays and events, like the time for fasting each year and the season for the big pilgrimage called the Hajj. Even though many countries with mostly Muslim people use the Gregorian calendar for everyday life, they still use the Hijri calendar for religious activities.

The Hijri calendar starts from a very important event that happened in the year 622 CE, when Muhammad and his followers moved from Mecca to Medina. This move is called the Hijrah and marks the beginning of the Islamic New Year. Today, we often write the year in this calendar with the letters AH, which stands for "Anno Hegirae," meaning "In the year of the Hijrah." As of 26 June 2025 CE, we are in the year 1447 AH, which will continue until about 15 June 2026.

History

For a list of Islamic centuries and the corresponding Gregorian years, see Timeline of Islamic history.

Pre-Islamic calendar

Main article: Pre-Islamic calendar

In ancient times, people in central Arabia, especially in Mecca, did not leave many written records. But we know from later Muslim writers that they used different calendars. Some of these calendars followed both the moon and the sun. The Arabs had special months when fighting was not allowed. These were Rajab and three months around the time of pilgrimage: Dhu'l-Qa'da, Dhu'l-Hijja, and Muharram.

Prohibiting Nasī'

Further information: Nasi'

In the tenth year after starting the Islamic calendar, Muslims believe God told them to stop a practice called Nasī'. This practice involved moving the holy months around. Stopping this practice helped make the calendar more fair and clear for everyone.

The three holy months are Dhu'l-Qa'da, Dhu'l-Hijja, and Muharram. The single holy month is Rajab. These months were important in both the old and the new calendars.

Days of the week

In the Islamic calendar, each day starts at sunset and ends at the next sunset. The days of the week are mostly named based on their order.

The sixth day is called the "gathering day" (Yawm al-Jumʿah), when Muslims meet for a special prayer at a mosque around noon. This day is often a day off for many people. Some countries make both Friday and Saturday days off, while others have Saturday and Sunday off but give people a long break on Friday to pray.

Months

Each month in the Islamic calendar starts when a new moon cycle begins. People look for the thin shape of the moon to know when a new month starts. Because of this, each month can have either 29 or 30 days, depending on when the moon can be seen and other conditions.

Four months are special and no fighting is allowed during them. These months are Rajab (the 7th month), and three months that follow one after another: Ḏū l-Qaʿda (the 11th month), Ḏū l-Ḥijja (the 12th month), and Muḥarram (the 1st month).

Alternative names

Afghan lunar calendar

The "Afghan lunar calendar" has two sets of names for the months, used by the Pashtuns and the Hazaras. These names were used until the time of Amanullah Khan, when the Solar Hijri Calendar became the official calendar in Afghanistan.

Turki lunar calendar

In Xinjiang, the Uyghur Muslims had their own names for the months. These names were used until they switched to the Gregorian calendar in the 1900s.

Alternative order

Twelver Shia Muslims believe the Islamic new year and the first month is Rabi' al-Awwal, not Muḥarram. They think this is the month when the Hijrah happened. Because of this, there are different ways of counting the years for some events, like the battle of Karbala. Shias say it happened in 60 AH, while Sunnis say it was in 61 AH.

Length of year

A regular year has 365.24219 days, but a lunar month averages about 29.53 days. Because of this, a lunar year with twelve months is about 10.88 days shorter than a solar year. This means that each year, the months of the Islamic calendar move about eleven days earlier compared to the seasons. Over about 33 solar years, the lunar calendar cycles through all the seasons.

Year numbering

Main article: Hijri era

Before the Islamic calendar, people in Arabia named years after big events. For example, the year when a leader tried to destroy a special building with elephants was called the Year of the Elephant. This is when the prophet Muhammad was born, around the year 570 CE.

Later, leaders decided to create a new way to number years. They chose the year when Muhammad moved to a city called Medina as the start of their calendar. This new calendar is called the Hijri calendar. It begins with a month called Muharram, following old Arab traditions. This helped people keep track of important dates and events.

Astronomical considerations

The Islamic calendar depends on watching the moon to decide when each month starts. This can make the dates change a little bit compared to a calendar that uses exact science to track the moon. Even with these small changes, the Islamic calendar stays very close to the science-based moon calendar, usually only differening by a few days.

Both the Islamic calendar and the science-based moon calendar do not follow the seasons, because they are based only on the moon, not the sun. The science-based moon calendar is 354.37 days long and starts each month when the moon is exactly between the Earth and the sun. The Islamic calendar also has months that are either 29 or 30 days, but because it relies on people actually seeing the moon, the pattern of 29 and 30 day months can seem random. In most places that use the Islamic calendar, people still look for the moon to decide when a month begins. Countries like Saudi Arabia have special groups to watch for the moon, but sometimes less experienced people also share what they see.

Because the moon can be seen at different times depending on where you are and the weather, different countries may start their months on different days. Some countries, like Malaysia and Indonesia, use specific rules about when the moon appears to decide the start of each month. Even though there are these differences, the Islamic calendar is mostly used for religious events, while most everyday activities still follow the Gregorian calendar used in many parts of the world.

Theological considerations

Some Muslims think it is okay to use science to know when each month starts, while others think they should only watch for the new moon in the sky, just like Muhammad did.

Many teachers of Islamic law think using science is fine. They say Muhammad’s way was for the people living then, and using science today is also okay. Some important groups agreed to use science to find out when months begin.

But in France, some Muslim groups changed to use science, but later decided to follow what Saudi Arabia announced instead. This caused some disagreement in the Muslim community there.

Calculated Islamic calendars

Islamic calendar of Turkey

Turkish Muslims use a special Islamic calendar that is planned many years ahead by the Turkish Presidency of Religious Affairs. This calendar decides when each month starts based on when the thin moon would appear in the sky.

Saudi Arabia's Umm al-Qura calendar

Saudi Arabia uses a special calendar called Umm al-Qura for important dates. This calendar uses careful star and moon watching to decide when each month starts. Over time, the rules for this calendar have changed a little.

Before the year 1420 in the Islamic calendar, they looked at the moon's age at sunset in Riyadh to decide the start of each month. This sometimes meant they celebrated holidays earlier than other Muslim countries.

Later, they changed the rules to match what places like Malaysia and Indonesia used, looking at when the moon would set after sunset in Mecca.

Since the year 1423 in the Islamic calendar, they added another rule to make sure the moon had passed the sun by sunset, even if it was too bright to see right away.

In 2007, groups in North America and Europe decided to use the same calculation rules as Saudi Arabia to plan their religious dates far in advance, hoping to one day make all Muslim calendars the same.

In 2016, Saudi Arabia started using the Gregorian calendar for paying government workers but kept the Islamic calendar for religious events.

Other calendars using the Islamic era

The Solar Hijri calendar is a solar calendar used in Iran. It counts its years from the Hijra, which is the migration of Muhammad from Mecca to Medina in 622 CE.

Tabular Islamic calendar

Main article: Tabular Islamic calendar

The Tabular Islamic calendar is a special way to figure out the Islamic calendar using math rules instead of watching the moon. It follows a 30-year pattern with 11 extra days and 19 normal days each year. Over a very long time, it stays almost exactly right, being off by just one day every 2,500 years.

Microsoft uses a version of this calendar called the "Kuwaiti algorithm" to change dates from the Gregorian calendar to the Islamic calendar. Microsoft says this method is based on old data from Kuwait, and it works like a known math calendar.

Notable dates

Main article: Muslim holidays

The Islamic, or Hijri, calendar marks several important days each year. These include:

• 1 Muharram: The Islamic New Year.
• 10 Muharram: A day remembering important events, such as the crossing of the Red Sea by Moses.
• 12 Rabi al-Awwal: The birthday of the Prophet Muhammad for many Muslims.
• 1 Ramadan: The start of the holy month of fasting.
• 1 Shawwal: Eid ul-Fitr, a joyful celebration marking the end of fasting.
• 8–13 Dhu'l-Hijja: The time for the Hajj pilgrimage to Mecca.
• 10 Dhu'l-Hijja: Eid al-Adha, another important celebration.

These days are special for Muslims around the world and help guide important religious practices and holidays.

Uses

The Islamic calendar is mainly used for religious events and important dates in Muslim countries. Because it follows the moon, it isn't good for farming, so in the past, people in these areas used other calendars for agriculture. For example, the Egyptian calendar was popular in many Islamic lands, and the Iranian calendar was used in Iran. In places like the Levant and Iraq, people still use old Aramaic names for months in everyday life. Today, most Muslim countries use the Gregorian calendar for everyday matters, but they keep the Islamic calendar for religious celebrations.

Some places mix calendars in special ways. For example, in Indonesia, the Javanese calendar blends parts of the Islamic calendar with older local traditions. In one country, there was even a unique calendar that counted years differently, making it hard for people to know the correct year.

Computer support

Later versions of Visual Basic and the .NET Framework offer support for the Islamic calendar. With the release of Java 8, this calendar is also included in its new Date and Time features.