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Islamic date difference calculator

Count the days, weeks, months and years between two dates, given on both the Islamic and Gregorian calendars so the two readings can be compared.

The two dates

Entered on which calendar

Defaults to today

Calendar reckoning

Tabular variant
Shift the result, in days

If the calendar where you are reads a day ahead of what this gives, set +1. The shift applies to every date the tool produces.

These dates are calculated, not announced

Islamic months begin on the sighting of the new crescent, announced locally. A converted date comes from a fixed arithmetic calendar instead, so it can differ from the observed one by a day in either direction, and countries differ from each other.

Saudi Arabia’s official Umm al-Qura calendar is a third scheme again. It is published as a table rather than derived from a formula, so it is not computed here.

Time between

Set both dates and the gap appears here, counted on both calendars.

One gap, two ways of saying it

The number of days between two dates is not open to interpretation. What changes between calendars is how those days get grouped into years and months, and the Islamic and Gregorian calendars group them quite differently.

A Hijri year runs about 354 days, eleven short of a solar one. Its months are 29 or 30 days rather than 28 to 31. So a gap of five solar years is five lunar years plus roughly an extra month and a half. Both descriptions are correct; they are counting in different units.

How the months are counted

Whole years come off first, then whole months, then whatever days remain. A month counts when the same day number comes round again, 10 Muharram to 10 Safar is one month whether that month held 29 days or 30. Where a day does not exist in the target month, the count clamps to the end of it rather than spilling over.

What the day count is good for

Days are the figure to use when precision matters: counting down to something, working out how long ago something happened, or checking a period expressed in days. The years-and-months reading is how people describe a span to each other, and it is the one to quote when the exact day is not the point.

Where the uncertainty actually sits

If you enter Gregorian dates, the answer is exact, every figure on the page follows from two dates that are not in dispute. The Hijri dates shown alongside them come from a fixed arithmetic calendar and may sit a day off the calendar announced where you are.

If you enter Hijri dates instead, that uncertainty moves into the answer itself, because the tool has to convert them before it can count. Where a day matters, enter the Gregorian dates.

What this will not settle

Some periods in Islamic law are counted in months, and which months, and from when, are not questions of arithmetic. This tool counts a gap between two dates you give it. It does not know which dates are the right ones to count between, and it is not the place to find out.

Questions

Why are the Hijri and Gregorian spans different if the day count is the same?
Because they are dividing the same days into differently sized boxes. A day is a day on both calendars, so the total never changes. But a Hijri year is about 354 days against a Gregorian 365, and Hijri months are 29 or 30 days rather than 28 to 31. The same gap therefore contains more lunar years and months than solar ones.
Does the order of the two dates matter?
No. If the second date comes before the first, the gap is measured between them the other way round and the tool says so. The number of days is the same in either direction.
How are the months counted?
Whole years first, then whole months, then the days left over. A month is counted when the same day of the month has come round again, so 10 Muharram to 10 Safar is one month regardless of whether that month ran 29 or 30 days. It is the way people read a span aloud rather than a fixed number of days.
Can I use this for a waiting period like iddah?
It will count the days and months accurately, but it cannot tell you which count applies. Waiting periods are defined in different terms depending on the circumstances, some in months, some in menstrual cycles, some running until a birth, and which one applies is a question for someone qualified, not for a date calculator.
Are the Hijri dates exact?
The gap is exact; the Hijri dates shown at either end are calculated from a fixed arithmetic calendar and may differ by a day from the announced calendar where you are. If you enter Gregorian dates, the day count is unaffected by that, only the Hijri labels move.

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