The Hijri calendar didn’t exist at the beginning of Islam. It emerged after an event happened during the judgment time of Umar ibn al-Khattab (may Allah be pleased with him), who is considered the first to use the Islamic calendar system.

The beginning of the story:

In the 17th year of the Hijra, a letter reached Abu Musa al-Ash’ari dated in Sha’ban. Then, he wrote to Caliph Umar ibn al-Khattab (may Allah be pleased with him), inquiring about letters that arrived dated by month without mentioning the year, which could lead to confusion between letters.

It was narrated from Sa’id ibn al-Musayyib (may Allah be pleased with him) that he said: “Umar gathered the people and asked them: ‘From which day should we start the Hijri Calendar? So, Ali ibn Abi Talib said: ‘From the day the Messenger of Allah (peace and blessings be upon him) emigrated and left the land of Mecca.’ So, Umar (may Allah be pleased with him) acted upon this.

In another narration:

Ibn Hajar said in Fath al-Bari: “They mentioned several reasons why Umar established the Islamic date. Among them is what Abu Nu’aim transmitted in his history: ‘That Abu Musa wrote to Umar: “We receive letters from you that have not been dated by a year.” So, Umar gathered the people. Some of them said: “Date by the Prophetic mission (Al-Mab’ath),” and others said: “Date by the Hijri date.” Then Umar said: “The Hijra distinguished between truth and falsehood, so date by it.” That was in the year seventeen of the Hijra. When they agreed, some of them said: “Start with Ramadan.” Umar replied: “Rather, with Muharram, for it is when people return from their Hajj.” So, they agreed upon that.

The final agreement:

Muslims, after consultation, agreed to start the Islamic calendar from the year of the Hijra, making Muharram its first month. This was because Muharram was traditionally the first month of the Arabs. Thus, they designated the first year as the year of the Hijra and its beginning as Muharram, as was customary for them.

Ibn Kathir stated in “Al-Bidaya wa al-Nihaya” (The Beginning and the End): “The Companions (may Allah be pleased with them) agreed in the year sixteen or some say seventeen during the judgment of Umar, to make the beginning of the Islamic date from the year of the Hijra.

They started the Hijri Calendar from the beginning of Muharram because the firm intention to emigrate was made in that month, as the pledge of allegiance (Al-Bay’ah) occurred in Dhul-Hijjah, which preceded it, and the first crescent moon after that was Muharram. Also, it was when people returned from their Hajj pilgrimage, making it suitable as a starting point.

The difference between Hijri and Miladi Calendar

The Hijri calendar differs from the Miladi calendar in how months are calculated. The Hijri calendar is based on the moon’s revolution around the Earth, but the Gregorian calendar relies on the Earth’s revolution around the sun. This difference causes the number of days in a month to vary between 29 and 30 days in the Hijri calendar, while the Miladi months have a fixed number of days.

As a result of the difference between the Hijri for Miladi calendars, the Hijri year is approximately 11 days shorter than the solar year. This is why Islamic rituals and holidays occur at different seasons and at varying times.

The importance of the Hijri date for Muslims:

 The Hijri calendar is very important for Muslims, reminding them of their glorious history, including events like the Battle of Badr, the Conquest of Mecca, the Battle of al-Qadisiyyah, and other momentous occasions in the history of our Ummah.

Many Islamic legal rulings (fiqh) are tied to the lunar months, and it is the basis for timing acts of worship such as fasting, Zakat, and Hajj. Al-Qurtubi, in his interpretation of Allah’s saying: “Indeed, the number of months with Allah is twelve months” (Quran 9:36), stated: “This verse indicates that the obligation to link rulings, whether for worship or otherwise, must be with the months and years known to the Arabs, not the months considered by non-Arabs, Romans, or Copts.”

That is why it is so important for muslims to use Hijri dates and not to use Miladi dates only.