Calendar converter (Hijri, Hebrew, Persian, Julian)

How to convert a date between calendars

Calendars name the same day differently, so convert through a day count: find the date's Julian Day Number, then name that day in the target calendar. JDN 2,451,545 is 1 January 2000 Gregorian, 19 December 1999 Julian, 24 Ramadan 1420 AH and 23 Tevet 5760 in the Hebrew calendar.

The Julian Day Number counts days from 1 January 4713 BC in the Julian calendar; it is a count, not a Julian-calendar date. Subtracting two gives the days between dates: 15 January 2026 is JDN 2,461,056, 9,511 days after 1 January 2000.

Calendars covered and how each counts

• Gregorian: a leap day in years divisible by 4, except century years not divisible by 400. Dates before 15 October 1582 are proleptic, with the rules extended backwards. Years 1 to 9999 are covered.
• Julian: a leap day every fourth year, century years included, so Julian 29 February 1900 exists; it is Gregorian 13 March 1900. Conversions use E. G. Richards' arithmetic.
• Islamic, tabular (civil epoch): months alternate 30 and 29 days, and Dhu al-Hijjah gains a 30th day in years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29 of each 30-year cycle. Year 1 began on Friday 16 July 622 (Julian).
• Islamic, Umm al-Qura: Saudi Arabia's official calendar, read from ICU's tables for 1300 to 1600 AH (about 1882 to 2174 CE). Outside those years the tabular rule applies.
• Hebrew: a fixed lunisolar calendar. Years 3, 6, 8, 11, 14, 17 and 19 of each 19-year cycle add a month, Adar I, so a year has 353 to 355 or 383 to 385 days.
• Hebrew years: counted from 7 October 3761 BC (Julian). Each begins at Rosh Hashanah, which falls between 5 September and 5 October.
• Persian (Solar Hijri): the year begins at Nowruz, on 20, 21 or 22 March, and counts from 622 CE. The first six months have 31 days, the next five 30, and Esfand 29, or 30 in a leap year.
• Indian national (Saka): 1 Chaitra falls on 22 March, or 21 March in a Gregorian leap year. Chaitra has 30 days (31 in leap years), the next five months 31 and the last six 30. The Saka year is the Gregorian year minus 78, or minus 79 before 1 Chaitra.

The Islamic, Hebrew, Persian and Indian dates come from the calendar engines described in ICU's calendar documentation. Hebrew 5784 was a leap year: 15 March 2024 was 5 Adar II 5784, as the Hebcal converter confirms.

Gregorian and Julian dates with their day numbers

Julian 4 October 1582 and Gregorian 15 October 1582 are consecutive days, JDN 2299160 and 2299161: the reform skipped ten dates, not ten days. The US Naval Observatory's Julian date notes keep that day count separate from calendar dates.

Julian to Gregorian by hand

For a Julian date in March to December of year Y, add ⌊Y ÷ 100⌋ − ⌊Y ÷ 400⌋ − 2 days to get the Gregorian date. For January and February, use Y − 1.

For 11 February 1732, use 1731: 17 − 4 − 2 = 11 days, so the Gregorian date is 22 February 1732. For 2026 the gap is 20 − 5 − 2 = 13 days, as in the 2 January and 15 January row above.

Old Style dates can carry the wrong year

Until 1752, England and its colonies began the legal year on 25 March, so a date from 1 January to 24 March carried the previous year's number. George Washington was born on 11 February 1731 Old Style, which is 22 February 1732 New Style.

Enter such a date with the year counted from 1 January, 1732-02-11. Entering 1731-02-11 gives 22 February 1731, a year too early.

Mistakes with Hijri and Hebrew dates

• Expecting the observed Islamic date. Where a month starts with a sighting of the new moon, it can begin a day or two away from the Umm al-Qura date.
• Mixing the two Islamic calendars. On 26 June 2025 Umm al-Qura gives 1 Muharram 1447, while the tabular calendar gives 29 Dhu al-Hijjah 1446.
• Forgetting that the day starts at sunset. Hebrew and Islamic dates change at sunset, so an evening event falls on the next date. Each conversion names the date in force during the daytime of the Gregorian date.
• Going back before a calendar began. There is no Islamic or Persian date before 622 CE and no Saka date before March 79 CE.

What you can enter

• A Gregorian date or a Julian date; the other calendars are results only.
• Julian dates as YYYY-MM-DD. Julian 29 February is valid in every year divisible by 4.
• Dates whose Gregorian year is between 1 and 9999.

To count the days between two Gregorian dates, use the date difference calculator. The day of the week calculator names the weekday of any Gregorian date.