How Many Days Are in a Hijri Year and Month?

How Many Days Are in a Hijri Year?

A Hijri year has twelve lunar months. In the tabular civil calendar, a common year has 354 days and a leap year has 355 days. The Wikipedia article on the Islamic calendar gives the same range of 354 or 355 days.

The Gregorian year is longer. It averages 365.2425 days, so a Hijri year runs about 11 days short of it.

Why Is the Hijri Year 354 Days?

The moon takes about 29.530589 days to pass from one new moon to the next. A month must be a whole number of days, so it is either 29 or 30.

Twelve months of 29.530589 days come to 354.367 days. The Wikipedia article on the Hijri year gives the mean lunar year as 354.367 days.

The Simple Count

• Six months of 30 days give 180 days.
• Six months of 29 days give 174 days.
• Together they make 180 + 174 = 354 days.

A common year of 354 days is therefore just six long months and six short ones.

What Is the Leap-Year Rule?

A year of 354 days falls a little short of 354.367. The missing part is 0.367 of a day each year. The tabular calendar collects it into leap days.

Over 30 years, 0.367 × 30 = 11.0 days. So the calendar adds 11 leap days in every 30 years, which is how the 355-day year arises.

Leap years are frequent in this scheme. Eleven in 30 is about 37 percent of years. In the Gregorian calendar, 97 years in 400 are leap years, or about 24 percent.

The Hijri leftover is 0.367 of a day a year. The Gregorian leftover is 0.2425 of a day, so it needs fewer leap days. That is why Hijri leap years come more often.

The same counting idea applies to every year in the cycle. Each year is a whole number of days, and the cycle repeats exactly every 30 years.

Once you know the start year of a cycle, the next cycle follows the same pattern of leap years. This is why one short rule is enough.

Which Years Are Leap Years?

The common Kuwaiti scheme uses years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29. Wikipedia lists this scheme in its tabular calendar article.

You can test any year with one rule. Year Y is a leap year when (11 × Y + 14) mod 30 is less than 11.

1. Take 1447. Multiply: 11 × 1447 = 15,917. Add 14 to get 15,931.
2. Divide by 30 and keep the remainder. 15,931 mod 30 = 1.
3. The remainder 1 is less than 11, so 1447 is a leap year of 355 days.
4. Take 1448. Multiply: 11 × 1448 = 15,928. Add 14 to get 15,942, and 15,942 mod 30 = 12.
5. The remainder 12 is not less than 11, so 1448 is a common year of 354 days.

The full cycle holds 30 × 354 + 11 = 10,631 days. The date checks below agree with this.

A Check Against Dates

In the tabular civil count, 1 Muharram 1447 AH falls on 27 June 2025. The next 1 Muharram, in 1448 AH, falls on 17 June 2026.

The gap between those two Gregorian dates is exactly 355 days. That matches a leap year of 355 days.

Two more dates anchor the count. Year 1 starts on 16 July 622 in the Julian calendar, or 19 July 622 in the Gregorian one. And 1 Muharram 1400 AH is 21 November 1979, the date given by Wikipedia.

How Many Days Are in a Hijri Month?

In the tabular calendar, odd-numbered months have 30 days and even-numbered months have 29. In a leap year, the twelfth month gains a thirtieth day.

The Wikipedia article on the tabular calendar states this rule. The table lists a common year (1448) and a leap year (1447) side by side.

The average of 30 and 29 is 29.5 days. The true lunar month is 29.530589 days, so the alternating pattern is very close to the moon.

Month names are covered on the Hijri months page. Spellings differ by language, but the order and lengths do not.

Is the Count the Same in Every Hijri Calendar?

The range of 354 or 355 days holds in general, but the way each month is fixed differs. There are three common methods, and they are explained in full on the calendar systems page.

• Tabular: a fixed pattern of 30 and 29 days, with a leap day in the twelfth month. Every year length is known in advance.
• Umm al-Qura: calculated from the moon for Mecca and published as a table. A month can have 29 or 30 days, and the order is not a strict alternation.
• Sighting: a month ends when the new crescent is seen. If it is not seen after day 29, the month runs to 30 days.

So a month is 29 or 30 days in all three. Only the tabular calendar lets you work out a given year or month length with simple arithmetic.

R.H. van Gent notes that sighted dates can differ from Umm al-Qura dates by one to three days. That is why a printed date and a local announcement can disagree.

How Does the Hijri Year Compare With the Gregorian Year?

The Gregorian year averages 365.2425 days. The tabular Hijri year averages 10,631 ÷ 30 = 354.37 days, so the difference is 10.88 days a year.

After 33 years the gap adds up to about 359 days, which is nearly a full Gregorian year. Wikipedia says the Hijri months move through the seasons over about 33 years.

Weeks and Days

A common year of 354 days is 50 weeks and 4 days. A leap year of 355 days is 50 weeks and 5 days. So a given Hijri date moves forward by 4 or 5 weekdays each year.

For converting a whole year to the Gregorian count, see the Hijri to Gregorian formula page. For where the count begins, see the page on year one.

How Do You Count Days Between Two Hijri Dates?

Add the month lengths from the table. The tabular calendar makes this a plain sum, which is a good test of the rules above.

From Muharram to Ramadan

Take a common year such as 1448. The first eight months have these lengths: 30, 29, 30, 29, 30, 29, 30 and 29.

Their sum is 236 days. So 1 Ramadan falls 236 days after 1 Muharram, and it is day 237 of the year.

From Muharram to Muharram

A full year gives the whole count. Start at 1 Muharram 1448, which is 17 June 2026. One common year of 354 days later, 1 Muharram 1449 falls on 6 June 2027.

Year 1449 is year 9 of its cycle, since 1449 = 48 × 30 + 9. Its leap test gives (11 × 1449 + 14) mod 30 = 23, so it is a common year.

How Do the Three Methods Compare at a Glance?

The table puts the points above side by side. It describes how each method fixes a length, not which one is right for any purpose.

The year range in the last two rows comes from the general statement in the Islamic calendar article. It does not list a separate rule for each of them.

What Mistakes Do People Make With Hijri Lengths?

A few slips come up again and again. Each one is easy to avoid once you know the numbers.

• Using 30 days for every month. Twelve months of 30 days make 360, which is far above the true 354.37.
• Using 365 for the Hijri year. That value belongs to the Gregorian calendar and overstates the Hijri year by 11 days.
• Treating 354.37 as a real year. It is an average. No year has a fraction of a day, so real years are 354 or 355.
• Mixing variants. A tabular month length cannot be applied to a date taken from a sighted or Umm al-Qura source.

Why the Average Is Not a Year Length

The figure 354.367 is the mean of many years. A single year holds whole days. The calendar rounds down to 354 and adds a day when the leftover grows.

The same idea runs the Gregorian calendar. Its average of 365.2425 days is not a real year either. A leap day in February absorbs the leftover.

Why Does the Length Matter for Old Dates?

A date in a letter or an inscription names a Hijri day. To place it on a modern calendar you must add up the days since a known anchor.

If the count uses 354 days for every year, the answer drifts by 11 days in 30 years. The leap rule removes that drift, which is why it appears in every converter.

A one-day error is still possible in any variant. For that reason, a converted date should name the method it used.

What Should You Remember?

• A month is 29 or 30 days, and a year is 354 or 355 days.
• The tabular leap rule adds 11 leap days in 30 years, which gives 10,631 days.
• The tabular calendar uses a pattern, while Umm al-Qura and sighting follow the moon.

Nothing here decides which day is correct for any observance. It only explains how the lengths are counted. The whole cluster is on the calendar hub.

Sources and Further Reading

• Tabular Islamic calendar, Wikipedia. The 354 and 355 day years, month lengths, the 10,631 day cycle and the Kuwaiti leap years.
• Hijri year, Wikipedia. The 354 to 355 day year and the mean lunar year of 354.367 days.
• Islamic calendar, Wikipedia. Months of 29 or 30 days, the three methods, the 10.88 day gap and 1 Muharram 1400 AH.
• The Umm al-Qura Calendar of Saudi Arabia, R.H. van Gent. A calculated calendar, with one to three day differences from sighted dates.
• Date checks and leap-year tests are computed in code. See the methodology.

Frequently Asked Questions