Hebrew Birthday Calculator — Jewish Calendar Date Finder

Convert your Gregorian birth date to the Hebrew calendar and find exactly when your next Hebrew birthday falls, using real lunisolar calendar math.

July 11, 2026

Your Birth Date (Gregorian calendar)

Gregorian-to-Hebrew date conversion is powered by the open-source @hebcal/core library — the same calculation engine behind Hebcal.com's official date converter — so the lunisolar math (19-year Metonic cycle, molad calculations, leap years, and Rosh Hashanah postponement rules) is astronomically accurate, not approximated. Your next Hebrew birthday's exact Gregorian date is found by locating the next occurrence of your Hebrew month and day going forward from today, following the standard Ashkenazic anniversary convention for birthdays that fall in Adar, Cheshvan, or Kislev — the three months whose length or existence can vary from year to year.

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Reference Values

Last verified: Jul 10, 2026

Category	Range	What It Means	Status
Hebrew calendar type ★	Lunisolar	Months follow the moon (29–30 days each), but a leap month is added in 7 of every 19 years to keep the calendar in sync with the solar year — so holidays like Passover always land in spring, not drifting through the seasons like a pure lunar calendar (e.g. the Islamic calendar) would.	★ Best
Metonic cycle ★	19-year cycle, 7 leap years	Years 3, 6, 8, 11, 14, 17, and 19 of the cycle are leap years with an extra month (Adar I) inserted before Adar. This 19-year pattern repeats indefinitely and is the mathematical backbone of the fixed Hebrew calendar used today.	★ Best
Hebrew year length	353–385 days	Unlike the Gregorian year's fixed 365 (or 366) days, a Hebrew year can be 353, 354, 355, 383, 384, or 385 days long depending on whether it's a leap year and whether Cheshvan and Kislev are "short" (29 days) or "long" (30 days) that year.	Good
Annual Gregorian drift	≈11 days/year, corrected in leap years	A 12-month Hebrew year is about 11 days shorter than a Gregorian year, so a birthday appears to move about 11 days earlier each year — until a leap year adds a whole extra month and pushes it about 30 days later, creating the back-and-forth wobble instead of one-directional drift.	Good
Birthday in Adar (non-leap year), landing on a leap year	Moves to Adar II	Standard Ashkenazic convention (per Reingold & Dershowitz, followed by Hebcal.com): someone born in the single Adar of an ordinary year observes their Hebrew birthday in Adar II — the last month of the year — whenever the current year is a leap year.	Okay
Birthday born in Adar I of a leap year	Same day, adjusted by year type	In a later leap year, the birthday falls on the same day in Adar I. In a later ordinary year (no Adar I exists), it falls on the same day in the single Adar.	Okay
Birthday on Cheshvan 30 or Kislev 30	Postponed to the 1st of the next month in short years	Cheshvan and Kislev vary between 29 and 30 days year to year. If someone was born on the 30th and the current Hebrew year's version of that month only has 29 days, the birthday shifts to the 1st of the following month instead.	Poor
Conversion method used by this calculator ★	@hebcal/core (HDate class)	This calculator does not hand-calculate the lunisolar conversion — it uses the open-source @hebcal/core library, the same calculation engine that powers Hebcal.com's official Hebrew date converter, to guarantee an astronomically correct date every time.	★ Best

Source: Hebrew calendar structure and Metonic cycle: Hebcal.com ("How the Hebrew Calendar Works," hebcal.com) and Chabad.org ("How the Jewish Calendar Works," chabad.org). Birthday/anniversary observance rules: Hebcal.com, "How does Hebcal determine anniversaries (birthdays, yahrzeits) in Adar, Cheshvan, or Kislev?" — citing Reingold & Dershowitz, Calendrical Calculations, p. 111 (Ashkenazic practice). Conversion engine: @hebcal/core npm package documentation.

Worked Examples

Standard Case — Sivan Birthday

Birth Date (Gregorian): June 15, 1990
Today: July 10, 2026

Hebrew birth date: 22 Sivan, 5750 — Next Hebrew birthday: Sunday, June 27, 2027 (22 Sivan, 5787)

Sivan is a regular month unaffected by leap-year month shifts, so the Hebrew day and month (22 Sivan) stay fixed every year — only the matching Gregorian date moves. Since Sivan has already passed in the current Hebrew year (5786) by the time this is checked, the next occurrence falls in Hebrew year 5787, turning this person's 37th Hebrew birthday.

Near-Realignment — Cheshvan Birthday

Birth Date (Gregorian): November 2, 1988
Today: July 10, 2026

Hebrew birth date: 22 Cheshvan, 5749 — Next Hebrew birthday: Monday, November 2, 2026 (22 Cheshvan, 5787)

This is a case where the Gregorian date happens to land back on November 2 — the same calendar date as the original birth. That's not a rule, just a coincidence of where this particular Hebrew year falls; the date will drift away from November 2 again in following years. It shows why the Hebrew calendar wobbles around the original date instead of drifting in one direction forever, the way a pure lunar calendar (with no leap months) would.

Leap-Year Adjustment — Adar Birthday

Birth Date (Gregorian): February 25, 1996
Today: July 10, 2026

Hebrew birth date: 5 Adar, 5756 (ordinary year) — Next Hebrew birthday: Sunday, March 14, 2027 (5 Adar II, 5787)

This person was born in the single Adar of an ordinary (non-leap) Hebrew year. Hebrew year 5787 is a leap year with two Adars, so by standard convention the birthday moves to Adar II — the last month of that year — rather than Adar I. That's why the matching Gregorian date jumps from late February to mid-March: a direct example of the leap-month drift this calculator is built to handle correctly.

Upcoming Soon — Elul Birthday

Birth Date (Gregorian): August 20, 1975
Today: July 10, 2026

Hebrew birth date: 13 Elul, 5735 — Next Hebrew birthday: Wednesday, August 26, 2026 (13 Elul, 5786)

Elul is the last month of the Hebrew year, right before Rosh Hashanah. Since Elul hasn't happened yet in the current Hebrew year (5786) as of this check, the next Hebrew birthday is only a few weeks away rather than more than a year out — turning this person's 51st Hebrew birthday.

How to Use This Calculator

1

Enter your Gregorian birth date

Pick your date of birth using the date field, entered on the regular Gregorian (Western) calendar you're used to.
2

See your Hebrew birth date

The calculator instantly converts it to the equivalent day, Hebrew month name, and Hebrew year (e.g. 22 Sivan, 5750).
3

Check your next Hebrew birthday

See the exact upcoming Gregorian date your next Hebrew birthday falls on, plus how many days away it is.
4

Track the drift year to year

Come back next year — the Gregorian date will have shifted, usually by 1-4 weeks, showing the lunisolar wobble in action.

What Each Value Means

Hebrew Date (Hebrew calendar date): A date on the Hebrew (Jewish) calendar, expressed as day, Hebrew month name, and Hebrew year (counted from the traditional Anno Mundi epoch, currently in the 5780s).
Next Hebrew Birthday (Gregorian date): The next upcoming Gregorian-calendar date on which your Hebrew birth month and day recur, found by converting forward from today's date using Hebrew calendar arithmetic.
Hebrew Age (years): The Hebrew year number you're turning on your next Hebrew birthday, counted the same way a regular age is counted — years elapsed since your Hebrew birth year.

Frequently Asked Questions

What is a Hebrew birthday?

It's the anniversary of your birth measured on the Hebrew (Jewish) calendar instead of the Gregorian calendar — the same Hebrew month and day you were born on, recurring every Hebrew year. Because the Hebrew calendar is lunisolar rather than solar, that Hebrew month-and-day combination lands on a different Gregorian date almost every year, unlike a regular birthday which stays fixed on the same Gregorian date.

Why does my Hebrew birthday move around on the Gregorian calendar?

The Hebrew calendar follows the moon: each month is 29 or 30 days, and 12 lunar months add up to about 354 days — roughly 11 days shorter than a 365-day Gregorian year. So a fixed Hebrew date drifts about 11 days earlier on the Gregorian calendar each year. To stop that drift from running away entirely (and to keep holidays like Passover in spring), the calendar inserts a leap month in 7 of every 19 years, which snaps the date back by about a month. The result is a wobble within a roughly 3-4 week band rather than a one-way drift.

How is the exact Hebrew date calculated?

This calculator uses @hebcal/core, an open-source JavaScript library that implements the full Hebrew calendar algorithm — the 19-year Metonic cycle, molad (new moon) calculations, leap year rules, and the four dechiyot (postponement) rules that determine exactly which day Rosh Hashanah falls on. It's the same calculation engine that powers Hebcal.com's own official date converter, so the conversion is astronomically precise rather than an approximation.

What happens if I was born in Adar, Cheshvan, or Kislev?

Those three months need special handling because they can vary from year to year. Adar sometimes splits into Adar I and Adar II in leap years, so a birthday in the single Adar of an ordinary year is conventionally observed in Adar II — the last month — during a leap year. Cheshvan and Kislev can each be either 29 or 30 days long depending on the year, so a birthday on the 30th of either month shifts to the 1st of the following month in a year where that 30th day doesn't exist. This calculator applies the standard Ashkenazic convention for all of these cases automatically.

Is this the same as astrology or numerology?

No. This is deterministic calendar arithmetic — converting one calendar system's date to another using well-defined mathematical rules, the same way converting Celsius to Fahrenheit is arithmetic, not prediction. There's no interpretation, no personality reading, and no fortune-telling involved. The Hebrew calendar itself is a real civil and religious calendar used for setting Jewish holidays, contracts, and legal documents in Israel and Jewish communities worldwide.