Every major civilization in human history has marked the flow of time by anchoring its calendar to a defining watershed moment. Ancient Rome dated its years from the founding of the city (Ab Urbe Condita). The Christian world counted from the estimated incarnation of Jesus Christ (Anno Domini). For the Islamic world, the entire architecture of time rests upon a momentous journey undertaken across the sunbaked Arabian desert in the seventh century: the Hijra of the Prophet Muhammad from Makkah to Madinah.
Yet, when curious readers ask the question: when did the Hijri calendar start, they often discover that the answer is richer and more surprising than a single calendar date. There are actually two distinct answers to this question. The first answer is the astronomical epoch from which the numbering begins: July 16, 622 CE. The second answer is the historical moment when the calendar was formally created, institutionalized, and adopted as official state policy: 638 CE (17 AH), during the caliphate of Umar ibn al-Khattab.
Understanding the difference between the physical migration and the administrative establishment of the calendar provides remarkable insight into early Islamic statecraft, astronomy, and theology. Whether you are checking today’s Hijri date, investigating what year it is in the Islamic calendar, or exploring our Hijri to Gregorian date converter, this guide traces the exact timeline of when and how the Islamic calendar began.
The Two Founding Dates: Epoch Versus Establishment
To understand the timeline of the Hijri calendar, one must clearly separate two historical realities: the retroactive starting point (the epoch) and the legislative decree that created the dating system.
During the lifetime of the Prophet Muhammad and the caliphate of Abu Bakr al-Siddiq, Muslims did not use a numbered numbering system for years. Following the traditional customs of the Arabian Peninsula, people referred to years by memorable public occurrences rather than consecutive integers. For example, the Prophet’s birth year was widely known as the Year of the Elephant (Am al-Fil), commemorating the failed military expedition against Makkah led by the Abyssinian ruler Abraha around 570 CE. Later years in Madinah were known by descriptive phrases such as the Year of the Permission to Fight, the Year of the Earthquake, or the Year of the Farewell Pilgrimage.
It was not until the fourth year of the caliphate of Umar ibn al-Khattab, corresponding to 17 AH (638 CE), that the expanding Islamic state confronted the practical necessity of a numbered, standardized calendar. When Umar and the senior Companions formally established the calendar, they did not start counting from year one of Umar’s reign, nor did they start from 638 CE. Instead, they backdated the calendar by sixteen years, setting the starting point at the year the Prophet arrived in Madinah.
✦ The Exact Founding Coordinates: When Did the Calendar Begin?
The Astronomical Epoch (1 Muharram 1 AH):
Friday, July 16, 622 CE (in the Julian calendar), corresponding to Julian Day 1,948,439.5.
The Prophet’s Arrival in Quba/Madinah:
12 Rabi al-Awwal 1 AH, corresponding to approximately September 24, 622 CE.
The Legislative Establishment of the System:
Jumada or Sha’ban in the year 17 AH (around April to August 638 CE), sixteen years after the migration took place.
The Bureaucratic Crisis in 17 AH That Triggered the Decision
The decision to institute an official calendar was driven by the rapid administrative expansion of the early Islamic state. Following the historic conquests of the Levant, Mesopotamia, and Persia, the caliph in Madinah governed vast territories stretching across modern-day Syria, Iraq, Egypt, and Iran. Provincial governors communicated with the central capital through written correspondence, financial receipts, tax decrees, and troop dispatches.
In the year 17 AH, Abu Musa al-Ash’ari, the governor of Basra in southern Iraq, sent an urgent diplomatic dispatch to Caliph Umar ibn al-Khattab in Madinah. The governor wrote: ‘Letters reach us from the Commander of the Faithful bearing dates such as the month of Sha’ban, but we do not know whether this refers to the current Sha’ban, the Sha’ban of last year, or the Sha’ban of next year. Debt contracts and treasury disbursements are falling into dispute because our documents lack an agreed calendar year.’
Around the same time, another legal dispute was brought before Umar involving a commercial debt. A contract stated that a financial obligation was due in the month of Sha’ban. When the creditor demanded payment, the debtor argued that the contract intended the Sha’ban of the following year. Umar realized that without a standardized year number, the legal system and the treasury (Bayt al-Mal) would descend into administrative chaos.
The Consultation of the Companions: Choosing the Starting Point
Faced with this challenge, Caliph Umar summoned the senior Companions in Madinah for an extraordinary Shura council. As recorded by classical historians including Al-Tabari and Ibn Kathir, several proposals were placed on the table:
Some attendees suggested adopting the calendar of the Persian Empire, while others recommended adopting the Roman calendar of the Byzantines. Umar rejected both ideas, insisting that the Muslim civilization must possess its own independent, indigenous dating system that reflected its spiritual identity and values.
Next, the council debated which milestone in the Prophet’s life should serve as the opening year:
A group suggested starting the calendar from the birth of the Prophet Muhammad (around 570 CE). However, this was rejected because the exact year and day of his birth were subjects of scholarly debate, and dating history from a birth mirrored the Christian calendar.
Another group proposed dating from the Prophet’s first divine revelation at the Cave of Hira (around 610 CE). Others suggested dating from the year of his death in 11 AH (632 CE). Umar objected to using the Prophet’s death, noting that it was a moment of profound national grief and sorrow for the community.
Finally, Ali ibn Abi Talib offered the decisive counsel: ‘Let us date time from the Hijra, for the migration was the event that separated truth from falsehood and marked the establishment of the Islamic state.’
Umar and the entire assembly agreed with enthusiasm. The migration was the turning point where Muslims transitioned from a persecuted, marginalized minority in Makkah to a self-governing, autonomous community in Madinah that could build institutions, sign international treaties, and protect the vulnerable.
✦ Why Was Muharram Chosen Instead of Rabi al-Awwal?
A fascinating historical detail often puzzles readers: the Prophet Muhammad actually arrived in the outskirts of Madinah during the month of Rabi al-Awwal (September 622 CE), not in Muharram.
Why, then, does the Hijri calendar begin with the first day of Muharram? When the council agreed on the Hijra, Uthman ibn Affan suggested: ‘Begin the calendar year with Muharram, for it is a sacred month, and it is the month wherein pilgrims return from the completion of their Hajj.’
Furthermore, the historical decision to undertake the migration was formulated during the Pledge of Aqaba in Dhul-Hijjah. The following month was Muharram, making it the true conceptual beginning of the migration journey. Therefore, the calendar was set to 1 Muharram of that same year, two months prior to the Prophet’s physical departure.
Historical Comparison of Ancient Calendar Eras
To place the founding of the Hijri calendar into global perspective, the table below compares the starting points, epochs, and founding contexts of major historical calendar systems:
| Calendar System | Starting Year (Epoch) | Foundational Milestone | Type of Calendar | Year Length |
|---|---|---|---|---|
| Hijri Calendar (AH) | July 16, 622 CE | The Hijra (Migration of the Prophet to Madinah) | Pure Lunar | ~354.37 days |
| Gregorian Calendar (CE/AD) | 1 CE (Calculated 525 CE) | Estimated Incarnation of Jesus Christ | Solar | 365.2425 days |
| Hebrew Calendar (AM) | 3761 BCE | Traditional Rabbinic date of Creation (Anno Mundi) | Lunisolar (Leap months added) | 353 to 385 days |
| Roman Calendar (AUC) | 753 BCE | Traditional founding of the city of Rome by Romulus | Lunisolar / Solar | 355 to 365 days |
| Persian Solar Hijri (SH) | March 21, 622 CE | The Hijra, but calculated on solar equinox cycles | Solar | 365.2422 days |
The Astronomical Coordinates of Day One
Astronomers and chronologists have examined the exact date of 1 Muharram 1 AH in relation to historical planetary alignments. In modern astronomical software and conversion algorithms, the epoch of the Islamic calendar is formally designated as the sunset of July 15, 622 CE, with the first daylight hours falling on Friday, July 16, 622 CE in the proleptic Julian calendar.
On that evening, the astronomical conjunction between the sun and moon had occurred two days earlier, and a very delicate crescent moon was theoretically present above the western horizon in Arabia. This date marks the foundational point from which every single Islamic date for the past fourteen centuries has been calculated. For deeper historical reading, explore our detailed companion chronicle on the history of the Hijri calendar under Umar ibn al-Khattab and the Hijra.
Because the Islamic calendar preserves a strict lunar rhythm without leap months, its years have remained completely free from arbitrary seasonal manipulations. To understand how this lunar engine functions, consult our comprehensive guide on how the Hijri calendar works, and explore our live overview of today’s Hijri date or convert specific milestones using our verified Hijri to Gregorian date converter.
Frequently Asked Questions About the Start of the Hijri Calendar
Was the Hijri calendar used during the life of the Prophet Muhammad?
The names and sacred status of the twelve lunar months were observed during the life of the Prophet Muhammad, but the consecutive numbering of years from the Hijra was established in 17 AH by Caliph Umar ibn al-Khattab.
Why is it called the Hijri calendar?
It is called the Hijri calendar because it takes the Hijra (the historic migration of the Prophet and his Companions from Makkah to Madinah) as its foundational baseline and year zero.
What Gregorian day was the first day of the Islamic calendar?
The first day of the Islamic calendar (1 Muharram 1 AH) corresponds to Friday, July 16, 622 CE in the Julian calendar.
How can I check the current Islamic year and date today?
You can check the live date, current month, and lunar phase on our today’s Hijri date page, or plan upcoming religious events on our Calendar 1447 AH page.