Yahrzeit calculator / Adar and leap years
Adar, leap years and the 30th of a month
Some Hebrew dates don't exist every year. Here's what the calculator shows in those years, what the sources say, and where the decision belongs to your rabbi.
Confirm with your rabbi. Communities differ on these cases. This page explains the calendar and quotes the sources named below; it doesn't decide which day your family keeps.
| Passing on | In a regular year | In a leap year | What the sources say |
|---|---|---|---|
| Adar, in a regular year | Adar | Adar I | Chabad.org: Adar I is the common custom; some communities keep Adar II; many, including Chabad, say Kaddish on both dates. |
| Adar I, in a leap year | Adar | Adar I | Chabad.org: the same Adar in leap years, Adar in regular years. |
| Adar II, in a leap year | Adar | Adar II | Chabad.org and Hebcal agree. |
| 30 Cheshvan | Depends on the year | Depends on the year | Cheshvan has 30 days only in some years. Hebcal’s rule looks at the first anniversary to choose the day in the other years. |
| 30 Kislev | Depends on the year | Depends on the year | The same as Cheshvan: Hebcal’s rule depends on the first anniversary. |
| 30 Adar I | 30 Shevat | 30 Adar I | Hebcal: the last day of Shevat in regular years. No other source we checked addresses this case. |
Sources: Hebcal developer docs, HebrewCalendar.getYahrzeit (opens in a new tab) (which cites Reingold and Dershowitz, Calendrical Calculations); Chabad.org, "In a Jewish Leap Year, During Which Adar Do I Observe Yahrtzeit?" (opens in a new tab) · checked 4 Oct 2026
Why there are two Adars
Seven years in every nineteen add a 13th month so the calendar keeps pace with the seasons. In those years Adar I (30 days) comes before Adar II (29 days). Cheshvan and Kislev also have 29 days in some years and 30 in others.
Source: Wikipedia, "Hebrew calendar" (opens in a new tab) · checked 4 Oct 2026
Where the disagreement comes from
Chabad.org traces it to a Talmudic discussion about which Adar is the "real" one. Maimonides rules that Adar II is primary, while the principle of doing a mitzvah at the first opportunity favours Adar I. That is why customs differ, and why many say Kaddish on both.
Source: Chabad.org, "In a Jewish Leap Year, During Which Adar Do I Observe Yahrtzeit?" (opens in a new tab) · checked 4 Oct 2026
What the calculator does
The table follows Hebcal's published yahrzeit rules for every year, and any result in these cases carries a short note saying so, with a link back here. The printable card carries the same note, so the shul office sees it too.
Find the yahrzeit dates
The Hebrew date of passing, the next ten yahrzeits with the evening each begins, a calendar file and a printable card.
