The Dawoodi Bohra (Fatimid) Hijri calendar

The Dawoodi Bohra community follows a tabular Hijri calendar: every date is fixed by arithmetic, not by sighting the moon. Months alternate 30 and 29 days, and Dhu al-Hijjah gains a 30th day in 11 years out of every 30.

That is the whole specification. The three numbers below reproduce it exactly, and this page computes them from the same code that schedules Admonere’s reminders — so what you read here is what the reminders actually fire on.

Epoch (1 Muharram 1 AH)
Julian Day 1948439 — Thursday 15 July 622 CE in the Julian calendar, which is 18 July 622 in the proleptic Gregorian calendar. Both dates name the same day; sources disagree only about which calendar they are quoting.
Month lengths
Strict 30 / 29 alternation from Muharram. Dhu al-Hijjah is 29 days, or 30 in a leap year.
Leap years
Years 2, 5, 8, 10, 13, 16, 19, 21, 24, 27, 29 of each 30-year cycle — 11 leap years per cycle.
Year length
354 days common, 355 leap. One cycle is exactly 10,631 days, a mean year of 354.3667 days.

Today in the Hijri calendar

Thursday, 17 September 2026 (Julian Day 2461301), computed in Asia/Kolkata. Each row applies a different tabular variant to the same day.

Same Gregorian day, five tabular calendars. The spread is why "the Hijri date" is ambiguous without naming a calendar.
CalendarDateEpoch (JD)
Dawoodi Bohra (Fatimid) Admonere default 6 Rabi' al-Thani 1448 AH 1948439
Islamic Civil (Kuwaiti) 4 Rabi' al-Thani 1448 AH 1948440
Islamic Tabular 5 Rabi' al-Thani 1448 AH 1948439
Tabular — Type I (Kushyar) 4 Rabi' al-Thani 1448 AH 1948440
Tabular — Type IV (Habash) 5 Rabi' al-Thani 1448 AH 1948440

The months

Month lengths. Only Dhu al-Hijjah varies, and only in a leap year (1448 AH shown).
#MonthCommon yearLeap year
1Muharram 3030
2Safar 2929
3Rabi' al-Awwal 3030
4Rabi' al-Thani 2929
5Jumada al-Awwal 3030
6Jumada al-Thani 2929
7Rajab 3030
8Sha'ban 2929
9Ramadan 3030
10Shawwal 2929
11Dhu al-Qi'dah 3030
12Dhu al-Hijjah 2930

Why “the Hijri date” is ambiguous

Several tabular calendars share the 30/29 alternation and the twelve month names, and differ only in their epoch and their leap set. Change either and the dates move. This is the usual reason two apps disagree by a day — not a bug in one of them, but two different calendars being asked the same question.

Every tabular variant is fully described by two numbers: where it starts, and which years of the 30-year cycle are leap years.
VariantEpoch — 1 Muharram 1 AHLeap years in the 30-year cycle
Dawoodi Bohra (Fatimid) 1948439
18 July 622 (proleptic Gregorian)		 2, 5, 8, 10, 13, 16, 19, 21, 24, 27, 29
Islamic Civil (Kuwaiti) 1948440
19 July 622 (proleptic Gregorian)		 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, 29
Islamic Tabular 1948439
18 July 622 (proleptic Gregorian)		 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, 29
Tabular — Type I (Kushyar) 1948440
19 July 622 (proleptic Gregorian)		 2, 5, 7, 10, 13, 15, 18, 21, 24, 26, 29
Tabular — Type IV (Habash) 1948440
19 July 622 (proleptic Gregorian)		 2, 5, 8, 11, 13, 16, 19, 21, 24, 27, 30

Admonere defaults to Dawoodi Bohra (Fatimid) and lets each account pick another variant, because a reminder on the wrong day is worse than no reminder.

Tabular is not astronomical

Umm al-Qura, the Saudi civil calendar, is a different kind of thing: it is computed from lunar visibility criteria and can be adjusted by announcement. A tabular calendar answers “what is the date in 40 years?” today; an astronomical one does not commit that far ahead in the same way. Because the difference between them varies from day to day, no fixed day-offset converts one into the other, and any tool that applies one is wrong roughly half the time.

This page describes the tabular calendars only. It is reference arithmetic, not a religious authority, and it is not an announcement of when a month begins.

Common questions

No. The Bohra/Fatimid calendar is arithmetic — every date for every year is fixed in advance by a formula. Umm al-Qura is astronomical, derived from computed lunar visibility, and is adjusted by decree. The two routinely land on different days, and the gap is not a constant offset, so you cannot convert between them by adding or subtracting a fixed number of days.

No. It is purely computed: months alternate 30 and 29 days, and Dhu al-Hijjah takes a 30th day in 11 of every 30 years. Because nothing is observed, dates years ahead are known exactly — which is what makes recurring reminders possible at all.

A common year is 354 days and a leap year 355. Over one 30-year cycle the calendar runs 10,631 days, a mean year of 354.3667 days — about 11 days shorter than a Gregorian year, which is why a Hijri anniversary drifts earlier through the Gregorian seasons.

Because they are running different calendars. Tabular variants differ in their epoch and in which cycle years are leap, so on any given day they can disagree by up to two days, and astronomical calendars diverge further still. A Hijri date is only unambiguous once the calendar it came from is named.

Reminders that recur on the Hijri date

Enter a Gregorian date once. Admonere stores the Hijri equivalent and reminds you every Hijri year — and can email the greeting for you on the day.

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