Dates and Days

Hebrew calendar

Your Hebrew birthday, and the civil date it lands on each year

The Hebrew calendar is the one calendar on this site that needs no astronomy at all: it has been fixed arithmetic since the fourth century, so every date here is exact rather than accurate to within something. Both directions convert, and every observance of the year is listed with the evening it begins — because a Hebrew day starts at sunset, and that is where most calculators quietly pick one answer.

Hebrew date of birth— Born in a leap year— Next occurrence— Years needing a convention—
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The years ahead — each Hebrew day begins at sunset the evening before
Hebrew dateCivil dateBegins evening ofConvention

Your Hebrew date does not move. The civil date does.

A Hebrew year is twelve lunar months, and twelve lunar months run about eleven days short of a solar year. Left alone the calendar would drift a whole season in a decade, so a thirteenth month is inserted seven times in every nineteen years. That is what makes a Hebrew birthday wander: the Hebrew date is fixed, and the civil date it lands on walks forward about eleven days a year and then jumps back roughly nineteen when the extra month arrives. Across a normal run of years the same birthday can sit anywhere in a three-week band, which is why converting one year at a time is such an unsatisfying way to plan.

The day starts the evening before

A Hebrew day begins at sunset. So a Hebrew birthday begins on the evening of the preceding civil day and runs to sunset on the date most calendars print. Ordinary usage usually means the evening; software usually means the daytime date. They are different days, and the table above prints both in labelled columns rather than picking one. If you are arranging anything around the date, say which one you mean — that single word removes nearly all the confusion these dates cause.

The months that sometimes run short

Cheshvan and Kislev are the two months whose length changes from year to year: each can run 29 or 30 days, and that is the mechanism the calendar uses to land its festivals on permitted weekdays. If you were born on the 30th of either, your birthday simply does not exist in a short year. This is not a rare curiosity. Over the next twenty Hebrew years there is no 30 Cheshvan in eleven of them and no 30 Kislev in five. Two practices are in use — keep the birthday on the last day of the short month, or move it to the first of the month that follows — and the table prints both, named, in every year where the question arises.

Adar, and the year with two of them

The inserted thirteenth month is a second Adar, so a leap year has Adar I and Adar II. A birthday from an ordinary Adar has to go somewhere, and both answers are followed: Adar II keeps it in the month immediately before Nisan, Adar I keeps the same month number. The gap between them is not a technicality — the two dates fall about a month apart. Seven of the next twenty Hebrew years are leap years, so anyone with an Adar birthday meets this more than a third of the time. Both are shown, labelled, every time.

What this page will not do

It will not tell you which practice is yours. Where a convention is genuinely disputed this site prints the alternatives and names them, the same way it prints the sunset boundary on the Hebrew calendar converter and the statutory-versus-observed split on the holidays page. The arithmetic here is exact — integer day counts from the calendar’s own rules, with no floating point and no approximation — and the choice of custom is yours.

Questions

What is my Hebrew birthday?
It is the Hebrew date you were born on, which the tool above works out from your civil date of birth. Because the Hebrew calendar is lunisolar and the civil one is not, that Hebrew date lands on a different civil date almost every year — commonly swinging across three weeks. The table shows where it falls for the years ahead rather than making you convert one at a time.
Why does my Hebrew birthday move around the civil calendar?
A Hebrew year is twelve lunar months, which runs about eleven days short of a solar year. A thirteenth month is added seven times in every nineteen to stop the calendar drifting through the seasons. Your Hebrew date is fixed; the civil date it maps to moves, and moves back sharply in the years that gain the extra month.
When does a Hebrew birthday actually begin?
At sunset on the evening before the daytime civil date. The table prints both, because ordinary usage means the evening and calendar software usually means the daytime date, and the two are different days. If you are arranging anything around it, quote which one you mean.
What happens if I was born on 30 Cheshvan or 30 Kislev?
Those months run either 29 or 30 days depending on the year, so in a short year the date does not exist at all. Over the next twenty Hebrew years there is no 30 Cheshvan in eleven of them and no 30 Kislev in five. Two practices are in use: keeping the birthday on the last day of the short month, or moving it to the first day of the month that follows. This page prints both and names them rather than picking one for you.
I was born in Adar. Which Adar is my birthday in a leap year?
A leap year has two, Adar I and Adar II, and a birthday from an ordinary Adar has to go in one of them. Both practices are followed: Adar II keeps the birthday in the month immediately before Nisan, while Adar I keeps the same month number. The difference is not small — the two dates fall about a month apart — so the table shows both, labelled, for every leap year in the range.