Hijri Calendar Explained: Lunar Months, Sunset Days, Sightings

The Hijri calendar is the calendar of Ramadan, the two Eids, Hajj and every other Islamic date. It is purely lunar, which makes it simple in one way (a month is one cycle of the moon) and confusing in another (it drifts through the seasons and depends on who is looking at the sky). This guide explains the pieces so that the dates on the Hijri converter and the Islamic calendar 2027 make sense.

Twelve lunar months

The Qur'an states that the number of months with Allah is twelve, and that four of them are sacred (9:36). The twelve months, in order, are Muharram, Safar, Rabi' al-Awwal, Rabi' al-Thani, Jumada al-Ula, Jumada al-Akhirah, Rajab, Sha'ban, Ramadan, Shawwal, Dhul Qa'dah and Dhul Hijjah. The Islamic months page explains the names.

A lunar month runs from one new crescent to the next. The real cycle (from one new moon to the next) averages 29.53 days, so a month is either 29 or 30 days, never fixed in advance like a Gregorian month. On average about half the months are 29 days and half are 30, but two or even three 30-day months can run in a row.

A year of about 354 days

Twelve lunar months come to 354 or 355 days. The solar year is 365 or 366. The difference, roughly 11 days, is why every Islamic date moves earlier each year:

Over about 33 Gregorian years, Ramadan passes through every season and comes back to the same dates. The same drift means a Hijri year number increases a little faster than the Gregorian one: 100 Gregorian years are about 103 Hijri years.

The Qur'an points to the moon's phases as the way to know the number of years and the reckoning (10:5), and describes the crescents as timings for people and for the Hajj (2:189). Nothing in the calendar is added to keep it aligned with the seasons; the drift is by design.

The day begins at sunset

In the Hijri calendar, the night belongs to the day that follows it. A new date begins at Maghrib. This has practical consequences:

• Ramadan: 1 Ramadan 1448 is expected on Monday 8 February 2027. The month begins at sunset on Sunday 7 February. The first tarawih is on Sunday evening; the first suhoor and the first fast are on Monday.
• The odd nights: the "27th night" of Ramadan is the night that comes before the 27th day, so it is the evening of Friday 5 March 2027, not the evening of 6 March.
• Eid: the night of Eid, with its takbir, is the evening before the Eid prayer.
• Jumu'ah: Friday in the Islamic sense begins at Maghrib on Thursday, which is why reading Surah al-Kahf on Friday can begin on Thursday evening.

Phone calendars and most printed timetables show the Hijri date against the Gregorian day; remember that the Hijri date actually changed the previous evening.

Umm al-Qura vs local sighting

There are two broad ways to decide when a month starts.

Calculated calendars. Saudi Arabia's Umm al-Qura calendar sets the first day of each month by a rule based on astronomy: the new moon (conjunction) must occur before sunset at Makkah, and the moon must set after the sun on that evening. Because the rule is mathematical, the calendar can be printed years ahead. Turkey's Diyanet, the Fiqh Council of North America and several European bodies use calculated criteria of their own.

Sighting-based calendars. Many countries announce the month only after people have physically seen the crescent, following the hadith to fast when you see it and break the fast when you see it, and to complete thirty days if it is hidden (Bukhari 1909 / Muslim 1081). Morocco, Pakistan, India, Bangladesh, Indonesia, Malaysia, Nigeria, South Africa and others run official sighting committees. Some communities accept a sighting anywhere in the world ("global sighting"), others only within their own country or region.

The two approaches agree most of the time and differ by one day a few times a year. Moon sighting explained goes into the astronomy behind why.

Which should you follow? Most scholars advise following your own country's authority or the masjid you pray in, so that a community fasts and celebrates together. Where schools and councils differ, ask a scholar or imam you trust.

Why our converter says "expected"

The Hijri date converter uses the Umm al-Qura calendar because it is the most widely used calculated calendar and the only one that can give a date for any day years ahead. But a calculated date is a forecast, not an announcement. On the evening of the 29th your local authority may declare the month complete at 30, and the Hijri date will then run one day behind the converter until the next month resets it.

That is why every date on this site carries the note: expected; the actual date in your country depends on moon sighting or the local authority and may differ by a day. For dates that matter (the first fast, Eid), check your local announcement.

Worked example: converting a date

Suppose you want the Hijri date of 20 February 2027.

1. 1 Ramadan 1448 is expected on 8 February 2027.
2. 20 February is 12 days after 8 February.
3. So 20 February is expected to be 13 Ramadan 1448 (the 8th is day 1, so add 12).
4. The 13th is the first of the white days (13, 14, 15), so 20–22 February 2027 are the white days of Ramadan, already covered by the Ramadan fast.

Now the reverse: if your country announced Ramadan on Tuesday 9 February instead, 20 February is 12 Ramadan for you, and the white days shift to 21–23 February. Every Hijri date in your country is anchored to that local announcement.

Reading a Hijri year number

1448 AH means 1448 lunar years since the Hijra, the migration of the Prophet (peace be upon him) from Makkah to Madinah in 622 CE. The calendar was formally adopted during the caliphate of Umar, who chose the Hijra as the starting point rather than the Prophet's birth or his first revelation. The Islamic New Year 1449 page covers this history.

A quick mental conversion: Gregorian year ≈ 622 + Hijri year × 0.97. For 1448: 622 + 1404 = 2026. For the Hijri year from a Gregorian one: (Gregorian − 622) × 1.03. For 2027: 1405 × 1.03 ≈ 1447, which is close; the exact year boundary in 2027 is 6 June, when 1449 begins.

Key facts in one table

Once these pieces are clear, the dates on the Islamic calendar 2027 page read naturally: each one is a calculated day that your community will confirm, one evening at a time, by looking at the sky.