Calendar Converter
11 calendar systems · Any date in history
Quick Dates
Select a date to see it in all calendar systems.
Calendar Systems Overview
From 14 March 1900 to 14 March 2100 the Julian calendar runs exactly 13 days behind the Gregorian, which is why Orthodox Christmas (25 December Julian) falls on 7 January. Pick any Gregorian date above and the converter shows it in 11 calendar systems at once, including Hebrew, Islamic, Persian, Ethiopian and Maya, using the published arithmetic rules for each.
Eleven major calendar systems are converted simultaneously. Each has its own epoch (starting point), year length, and month structure.
| Calendar | Type | Epoch / Start |
|---|---|---|
| Gregorian | Solar | 1 January 1 AD |
| Julian | Solar | 1 January 45 BC |
| Islamic (Hijri) | Lunar | 16 July 622 CE |
| Hebrew (Jewish) | Lunisolar | 7 October 3761 BCE |
| Persian (Solar Hijri) | Solar | 19 March 622 CE |
| Ethiopian | Solar | 29 August 8 CE |
| Coptic | Solar | 29 August 284 CE |
| Byzantine | Solar | 1 September 5509 BCE |
| Roman (Ab Urbe Condita) | Solar | 21 April 753 BC (Varronian) |
| Maya Long Count | Day count | 11 August 3114 BCE (proleptic Gregorian) |
| Unix Timestamp | Linear | 1 January 1970 CE |
Epoch dates before 1582 in the table above are Julian calendar dates unless marked.
Julian vs Gregorian: The Gap by Century
The Julian calendar keeps 29 February in every century year; the Gregorian skips it unless the year divides by 400. So the gap grows by one day after February in 1700, 1800, 1900 and 2100, but not in 2000.
| Gregorian dates | Julian is behind by |
|---|---|
| 15 Oct 1582 to 11 Mar 1700 | 10 days |
| 12 Mar 1700 to 12 Mar 1800 | 11 days |
| 13 Mar 1800 to 13 Mar 1900 | 12 days |
| 14 Mar 1900 to 14 Mar 2100 | 13 days |
| 15 Mar 2100 to 15 Mar 2200 | 14 days |
Before 1582 the gap is smaller: 9 days in 1453 and 6 days in 1066. Historical dates from those years are usually recorded in the Julian calendar, so add the gap before you enter them here. The Battle of Hastings (14 October 1066, Julian) is 20 October 1066 on the proleptic Gregorian calendar.
Key Dates in 2026 and 2027
Computed with the converter's own algorithms. Hebrew and Islamic days begin at sunset, so each holiday starts on the evening before the date shown.
| Event | Calendar date | Gregorian date |
|---|---|---|
| Ethiopian New Year | 1 Meskerem 2019 | Fri 11 Sep 2026 |
| Rosh Hashanah | 1 Tishri 5787 | Sat 12 Sep 2026 |
| Yom Kippur | 10 Tishri 5787 | Mon 21 Sep 2026 |
| Hanukkah, first day | 25 Kislev 5787 | Sat 5 Dec 2026 |
| Orthodox Christmas | 25 December 2026 (Julian) | Thu 7 Jan 2027 |
| Start of Ramadan | 1 Ramadan 1448 | Mon 8 Feb 2027 |
| Eid al-Fitr | 1 Shawwal 1448 | Tue 9 Mar 2027 (Umm al-Qura), Wed 10 Mar (tabular) |
| Nowruz (Persian New Year) | 1 Farvardin 1406 | Sun 21 Mar 2027 |
| Passover, first day | 15 Nisan 5787 | Thu 22 Apr 2027 |
| Islamic New Year | 1 Muharram 1449 | Sun 6 Jun 2027 |
| Ethiopian New Year | 1 Meskerem 2020 | Sun 12 Sep 2027 |
| Rosh Hashanah | 1 Tishri 5788 | Sat 2 Oct 2027 |
Islamic months officially begin when the new crescent is sighted, so the date announced in a given country can be a day later than the calculated one. For reference, Ramadan 1447 began on Wednesday 18 February 2026 in the Umm al-Qura calendar, the same day the tabular calendar gives.
How Each Calendar Is Calculated
- Julian Day Number. Every conversion goes through the JDN, a running count of days from 1 January 4713 BC (Julian). 21 September 2026 is JDN 2,461,305.
- Hebrew. The fixed arithmetic calendar: 19-year cycles with a 13th month in years 3, 6, 8, 11, 14, 17 and 19, the mean new moon (molad) of Tishri, and the postponement rules that keep Rosh Hashanah off Sunday, Wednesday and Friday. Years run 353 to 385 days.
- Islamic, two ways. The tabular calendar uses 30-year cycles of 12 lunar months with 11 leap years. The Umm al-Qura row is Saudi Arabia's official calendar, read from your browser's built-in calendar data.
- Persian. A 33-year arithmetic rule that reproduces the official Iranian calendar, where the year starts on the day of the March equinox (measured at Tehran), for 1800 to 2100.
- Ethiopian and Coptic. Twelve 30-day months plus a short 13th month of 5 or 6 days, with a leap year every fourth year. New Year falls on 11 September, or 12 September in the year before a Gregorian leap year.
- Byzantine and Roman. Both use Julian days and months. The Byzantine year starts on 1 September; the Roman year count starts at 753 BC.
- Maya Long Count. Uses the standard GMT correlation (JDN 584,283), so 13.0.0.0.0 is 21 December 2012.
The Hebrew, Islamic (tabular), Ethiopian, Coptic and Persian results were checked day by day from 1800 to 2200 against the Unicode CLDR calendar data built into modern browsers.
Method and sources. Algorithms from E. M. Reingold and N. Dershowitz, Calendrical Calculations (Cambridge University Press), for the Hebrew, tabular Islamic, Coptic and Ethiopian calendars; the 33-year Persian arithmetic of K. M. Borkowski (1996); the Julian Day Number conversions of Fliegel and Van Flandern (1968); the GMT correlation 584,283 for the Maya Long Count. Umm al-Qura dates come from the Unicode CLDR data in your browser. Results were cross-checked against the ICU/CLDR calendars for every day from 1800 to 2200.
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Calendar Questions
The Gregorian calendar, introduced by Pope Gregory XIII in 1582, corrects the Julian calendar by skipping 3 leap years every 400 years. The Julian calendar, established by Julius Caesar in 46 BC, adds a leap year every 4 years without exception, making it slightly too long. As of 2026, the Julian calendar is 13 days behind the Gregorian. Most of the world switched to Gregorian by the 20th century; Russia switched in 1918, Greece in 1923.
Orthodox churches that follow the Julian calendar (Russian, Serbian, Georgian Orthodox) celebrate Christmas on December 25 Julian, which falls on January 7 Gregorian. Churches that use the Revised Julian Calendar (Greek, Romanian, Bulgarian Orthodox) celebrate on December 25 Gregorian (same as Western Christmas). The difference comes from the 13-day gap between Julian and Gregorian calendars accumulated since the Council of Nicaea (325 AD).
The Islamic calendar is a purely lunar calendar of 12 months, each beginning with the new moon crescent. A lunar year is about 354 days (11 days shorter than the solar year), so Islamic dates shift approximately 11 days earlier each Gregorian year. This is why Ramadan and Eid move through all seasons. Year 1 AH (Anno Hegirae) corresponds to 622 CE, the year of Muhammad's migration from Mecca to Medina.
The Hebrew calendar is a lunisolar calendar: it tracks lunar months but adds a 13th leap month (Adar II) 7 times in every 19-year cycle (Metonic cycle) to stay aligned with the solar year. Year 1 AM (Anno Mundi) corresponds to 3761 BCE in the traditional Jewish reckoning of creation. The Hebrew calendar governs Jewish religious holidays: Rosh Hashanah, Yom Kippur, Passover, etc.
The Maya Long Count is a vigesimal (base-20) positional calendar counting days from the mythical Maya creation date (August 11, 3114 BCE in the proleptic Gregorian calendar). It uses five units: Baktun (144,000 days), Katun (7,200 days), Tun (360 days), Uinal (20 days), Kin (1 day). The famously misinterpreted "end date" of December 21, 2012 was simply the day the count reached 13.0.0.0.0, the end of the 13th baktun since the Maya creation date, much like a car odometer rolling over.
The Solar Hijri calendar (also called the Iranian or Jalali calendar) is the official calendar of Iran and Afghanistan. It is a solar calendar starting from the Hijra (622 CE) but using solar year length. The year begins at Nowruz (Persian New Year) on the spring equinox, around March 20 to 21 Gregorian. It is extremely accurate: more precise than the Gregorian calendar. The current year is 1405 SH, which began on 21 March 2026.
The Ethiopian calendar (Ge'ez calendar) is based on the Coptic calendar, which is derived from the ancient Egyptian calendar. It has 13 months: 12 months of 30 days and 1 intercalary month (Pagume) of 5 or 6 days. Ethiopia is approximately 7 to 8 years behind the Gregorian calendar (they celebrated the new millennium in 2007). Ethiopia uses its own year count, currently in the year 2019, which began on 11 September 2026.
The Byzantine calendar (also called the Creation Era or Anno Mundi) was used by the Eastern Roman (Byzantine) Empire and Orthodox Churches until the 18th century. Year 1 AM is September 1, 5509 BC, based on the Byzantine reckoning of the world's creation. The Byzantine New Year begins on September 1. Russia used this calendar until 1700, when Peter the Great switched to the Julian calendar (Soviet Russia then moved to the Gregorian calendar in 1918).
The Coptic calendar is used by the Coptic Orthodox Church of Egypt. It has 13 months (12 of 30 days, 1 of 5 to 6 days) and is derived from the ancient Egyptian calendar. Year 1 AM in the Coptic calendar corresponds to 284 CE (the accession of Emperor Diocletian, who persecuted Christians: called the "Era of Martyrs"). The current Coptic year is 1743 AM, which began on 11 September 2026. Easter and Coptic feasts are calculated in this system.
The Gregorian calendar is very accurate but not perfect. It has a year of 365.2425 days, compared to the solar year of 365.24219 days. The error is about 1 day every 3,200 years. The Gregorian reform in 1582 also corrected the accumulated 10-day error from centuries of Julian use by skipping October 5 to 14, 1582. The Persian Solar Hijri calendar does better still: each year starts on the day of the observed March equinox, so it cannot drift.
Rosh Hashanah 5787 begins at sunset on Friday 11 September 2026, and 1 Tishri 5787 is Saturday 12 September. Yom Kippur follows on 10 Tishri: it begins at sunset on Sunday 20 September and ends on Monday 21 September 2026. In 2027 Rosh Hashanah falls on Saturday 2 October.
The tabular Islamic calendar is purely arithmetic, with months of 29 and 30 days in a fixed pattern. The Umm al-Qura calendar is Saudi Arabia's official calendar, based on astronomical calculation of the new moon. They often agree but can differ by a day or two: on 21 September 2026 the tabular date is 8 Rabi al-Thani 1448 and the Umm al-Qura date is 10 Rabi al-Thani. Communities that wait for a sighting of the crescent may differ again.
Both the Umm al-Qura and the tabular calendars put 1 Ramadan 1448 on Monday 8 February 2027, so the first evening prayers (tarawih) are on Sunday 7 February. The end of the month differs: Eid al-Fitr is Tuesday 9 March 2027 in Umm al-Qura and Wednesday 10 March in the tabular calendar. Local moon sighting can move either date by a day.