Hebrew Date Converter
Convert any Gregorian date to its Hebrew (Jewish) calendar equivalent — year, month and day.
Calculator
This tool converts Gregorian → Hebrew only. The Hebrew calendar names its months (Tishrei, Nisan, and Adar I / Adar II in a leap year) rather than numbering them, so a numeric Hebrew date cannot be turned back into a single Gregorian day unambiguously.
About this calculator
This converter turns any Gregorian (civil) date into its date on the Hebrew — also called the Jewish — calendar: the year counted in Anno Mundi (AM), the month by name, the day, and the weekday. The Hebrew calendar is lunisolar, a hybrid of moon and sun. Its twelve months — Tishrei, Cheshvan, Kislev, Tevet, Shevat, Adar, Nisan, Iyar, Sivan, Tammuz, Av and Elul — each begin near a new moon, so a plain lunar year of about 354 days would slowly drift out of step with the seasons. To stop that drift, a whole leap MONTH (a second Adar) is added in seven years out of every nineteen, the Metonic cycle, which keeps Passover in spring and the autumn festivals in autumn. Enter a Gregorian year, month and day and read the Hebrew equivalent; by default the tool shows today’s date, so it doubles as a "what is today’s Hebrew date" lookup.
How to read your results
The headline result is your Gregorian date expressed on the Hebrew calendar — its day, its month name, and its year with the suffix AM (Anno Mundi, "in the year of the world"), the count from the traditional date of Creation. So Hebrew year 5784 AM overlaps Gregorian 2023–24 CE. Below it you get the weekday, which is the same real day of the week on both calendars because they describe the same 24-hour civil day, and a note on whether that Hebrew year is a common year (twelve months) or a leap year (thirteen, with the extra month shown as Adar I followed by Adar II). The Hebrew day actually begins at sunset the evening before; this tool reports the calendar date for the daytime, the convention used by date converters such as Hebcal.
How it's calculated
The conversion pivots on the Julian Day Number (JDN), a continuous count of days that is independent of any calendar. Your Gregorian date is first reduced to its JDN with the standard civil-date formula (rejecting impossible dates such as 31 February through a round-trip check), and that JDN is then read out in the Hebrew calendar via Intl.DateTimeFormat with the "ca-hebrew" calendar (the ICU implementation), which yields the Anno Mundi year, the month name and the day. The weekday is derived directly from the JDN, so it is identical for both calendars. Whether the Hebrew year is a leap year is computed from the Metonic rule — a year is a leap year when (year × 7 + 1) mod 19 is less than 7, i.e. when year mod 19 is 0, 3, 6, 8, 11, 14 or 17 — and a leap year is the one that carries the extra Adar. "Today" is read at local civil midnight in your time zone after the page loads, so the default date is correct wherever you are without baking a build-time date into the page.
Worked example
Convert 23 April 2024 (Gregorian) to the Hebrew calendar.
23 April 2024 CE comes out as 15 Nisan 5784 AM, a Tuesday — the first day of Passover (Pesach), which always falls on 15 Nisan. Because 5784 is one of the seven Metonic leap years in each nineteen-year cycle (5784 mod 19 = 8), that year carries thirteen months: a date such as 15 February 2024 lands in the inserted month, returning as 6 Adar I 5784, while 15 March 2024 falls in 5 Adar II 5784. In an ordinary twelve-month year there is just one "Adar" with no I/II suffix.
Frequently asked questions
Why do some Hebrew years have 13 months instead of 12?
Because the calendar is lunisolar. Twelve lunar months run about 354 days, eleven short of the solar year, so without a correction the months would slide backwards through the seasons. The fix is the Metonic cycle: in seven of every nineteen years a thirteenth month — a second Adar — is inserted, splitting the usual Adar into Adar I and Adar II. Those leap years keep Passover in spring and Rosh Hashanah in autumn. This converter labels each result as a common year (12 months) or a leap year (13 months).
What does the year mean — what is Anno Mundi (AM)?
Hebrew years are counted in Anno Mundi, Latin for "in the year of the world": a count from the traditional rabbinic date of Creation. That is why the numbers are so large — Hebrew year 5784 AM corresponds to Gregorian 2023–24 CE. The civil year turns on Rosh Hashanah, the new year, which falls on 1 Tishrei in September or October, so a single Gregorian year always straddles two Hebrew years.
Why does this tool only convert Gregorian → Hebrew, not the other way?
The Hebrew calendar identifies its months by NAME rather than by a fixed number — Tishrei, Cheshvan, Kislev, and so on — and in a leap year the single Adar becomes two months, Adar I and Adar II, which shifts the numbering. The underlying engine reads those months as Intl names with no reliable numeric index, so a numeric Hebrew year/month/day cannot be matched back to one Gregorian day without ambiguity. Converting the well-defined direction (Gregorian → Hebrew) avoids that, which is why the reverse is intentionally left out.
Why do month lengths and even the year length vary?
Two of the months, Cheshvan and Kislev, can each be 29 or 30 days, which makes a common year deficient (353 days), regular (354) or complete (355) — and a leap year correspondingly 383, 384 or 385. The exact pattern is set by the molad (the calculated new moon) together with postponement rules called dehiyyot, which adjust which weekday Rosh Hashanah is allowed to begin. The converter handles all of this through the standard Intl Hebrew calendar, so the result already reflects the right month lengths for that year.
Sources
Reviewed by the YouCalc Team · Last reviewed
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