Hebrew Calendar Converter
Convert dates between the Hebrew (Jewish) and Gregorian calendars. Includes Adar I/II in leap years and upcoming festival countdowns.
1 Tishrei 5787 AM
12 September 2026 CE
2026-09-12
תשפ״ז
5787
Adar II (leap year)
Year
AM 5787
Day of week
Saturday
Hebrew to Gregorian converter. Translate any date between the Jewish lunisolar and Gregorian calendars.
A Hebrew to Gregorian converter translates dates between the Jewish calendar and the Gregorian calendar. Enter the day, Hebrew month, and Hebrew year, and the tool returns the equivalent Gregorian date plus the day of the week, the Anno Mundi (AM) marker, the upcoming Jewish festivals, and Adar I/II disambiguation in leap years.
What Is the Hebrew Calendar?
The Hebrew calendar is a lunisolar calendar used in Judaism for religious holidays, Bar and Bat Mitzvah ceremonies, and the civil calendar of the State of Israel. Year numbering counts from the traditional date of creation in 3761 BCE, so the year 5786 AM corresponds to 2025–2026 CE.
The calendar has 12 months in common years and 13 in leap years, following a 19-year Metonic cycle (years 3, 6, 8, 11, 14, 17, 19 are leap). Months are Tishrei, Cheshvan, Kislev, Tevet, Shevat, Adar (or Adar I + Adar II in leap years), Nisan, Iyar, Sivan, Tammuz, Av, Elul.
The day starts at sunset, not midnight — so a date in this converter refers to the daylight portion of the corresponding civil day.
How to Convert Hebrew Dates
The Hebrew calendar uses a deterministic arithmetic algorithm finalized by Hillel II around 358 CE. Year 1 AM started Monday, 7 October 3761 BCE Julian proleptic.
1. Pick the conversion direction (Gregorian → Hebrew or Hebrew → Gregorian).
2. Enter the date in the origin calendar.
3. The tool computes via Julian Day pivot. Leap years automatically show 13 months in the dropdown (Adar I and Adar II appear instead of just Adar).
4. Output includes the upcoming Jewish festival, the day of the week, and the ISO-8601 representation.
Hebrew Year and Month Calculation
- = Predicate: true if year y is a leap year (13 months)
- = Hebrew year (Anno Mundi)
The Metonic cycle has 19 years, of which 7 are leap. Year length depends on the molad (mean conjunction of the moon) calculation and four postponement rules (dehiyyot) that determine when Rosh Hashanah falls.
Cheshvan and Kislev have variable lengths — 29 or 30 days each — which together produce six possible year types: deficient (353 / 383 days), regular (354 / 384), or complete (355 / 385). All other months have fixed lengths.
Hebrew Conversion Examples
Rosh Hashanah 5787
1 Tishrei 5787 AM ≈ 21 September 2026 (Gregorian sunset). Rosh Hashanah marks the start of the Hebrew civil year.
Pesach 5786
15 Nisan 5786 AM ≈ 2 April 2026 (Gregorian). Pesach (Passover) is one of the three pilgrimage festivals in Judaism.
Hanukkah 5786
25 Kislev 5786 AM ≈ 14 December 2025 (Gregorian). The Festival of Lights begins on 25 Kislev and lasts eight days.
Tips for Converting Hebrew Dates
- The Hebrew day starts at sunset, so converting 'today' to a Hebrew date around dusk may differ by one day.
- Leap years insert Adar I (30 days) before Adar II (29 days). Festivals like Purim move to Adar II in leap years.
- The Hebrew gematria for the year (e.g., 5786 → תשפ״ו) is shown when the locale is Hebrew.
- For Bar/Bat Mitzvah date calculation, the tool returns the Gregorian date corresponding to the 13th (or 12th for girls) Hebrew birthday.
- Days until the next major festival (Rosh Hashanah, Pesach, Hanukkah, Yom Kippur) are shown automatically.
Hebrew Calendar FAQ
What is Anno Mundi?
Anno Mundi (AM, 'in the year of the world') is the Hebrew era counting from the traditional date of creation. Year 1 AM corresponds to 3761 BCE.
Why does Adar sometimes appear twice?
In Hebrew leap years (7 of every 19), an extra month called Adar I is inserted before what would otherwise be the regular Adar (now called Adar II). This keeps the lunisolar calendar aligned with the solar year so Pesach always falls in spring.
How does the Hebrew calendar handle Cheshvan and Kislev variability?
These two months can be 29 or 30 days each depending on year type. The combination produces six possible year lengths (353/354/355 in common years, 383/384/385 in leap years), all determined by the molad calculation and the dehiyyot postponement rules.
Is this conversion accurate for ancient dates?
Yes — the Hebrew arithmetic calendar is deterministic, so the calculation is exact going back to year 1 AM. For dates with practical relevance, the supported range is roughly 3000-7000 AM.
What is the difference between Hebrew civil and ecclesiastical year?
The Hebrew civil year starts on 1 Tishrei (Rosh Hashanah). The ecclesiastical year starts on 1 Nisan, the month of Pesach. Year numbering increments on 1 Tishrei. This converter uses the civil convention.
Hebrew Calendar Glossary
Anno Mundi (AM)
Era marker for the Hebrew calendar; counts years from the traditional creation date in 3761 BCE.
Metonic cycle
A 19-year cycle in which 7 years are leap (have 13 months), keeping the lunisolar calendar aligned with the solar year.
Molad
The calculated mean conjunction of the moon (new moon) used to determine when each Hebrew month begins.
Dehiyyot
The four postponement rules applied to Rosh Hashanah to avoid certain unwanted day-of-week alignments.
Adar I / Adar II
In leap years, an extra month (Adar I, 30 days) is inserted before the normal Adar (now Adar II, 29 days).
Tishrei
The first month of the Hebrew civil year, containing Rosh Hashanah and Yom Kippur.
Pesach
Passover. Begins on 15 Nisan and commemorates the Exodus from Egypt.
Sources & References
- Hebrew calendar — the arithmetical calendar attributed to Hillel II that this converter implements: the 19-year Metonic cycle with leap years at positions 3, 6, 8, 11, 14, 17 and 19 (Adar I inserted before Adar II), year lengths of 353/354/355 or 383/384/385 days, and the four dehiyyot that postpone Rosh Hashanah.
- Hebcal date converter — the independent implementation this tool's epoch was checked against. That check caught a real bug: the epoch was two days low, which shifted every Rosh Hashanah lookup by two days until it was corrected in May 2026. 1 Tishrei AM 1 = 7 September 3761 BCE (proleptic Gregorian).
- Dershowitz and Reingold, Calendrical Calculations — the standard reference whose Hebrew-calendar algorithm this implementation follows, rewritten to be self-contained rather than pulled in as a dependency.
- Unicode LDML Part 4: Dates — the specification behind the hebrew calendar browsers expose through Intl, and the naming conventions used for the leap month.