Free tool
Convert Gregorian dates to Hebrew (and back), look up the next five yahrzeit observances for a memorial date, find this week's parashat ha-shavua, and see every major Jewish festival for the year.
21 Av 5786 (4 August 2026)
5786-05-21
כ״א אב ה׳תשפ״ו
The Hebrew calendar is lunisolar: months track the moon (29 or 30 days each) and a 13th month gets inserted seven times every 19 years to keep Pesach in spring. Gregorian is purely solar and adds a single leap day every four years. Both calendars roughly track the same solar cycle, but the start of the Hebrew year drifts across September and October depending on whether the previous year was full, regular, or short, and the start of the day is sundown, not midnight. So a "birthday" on 15 Cheshvan can sit on different Gregorian dates each year and the difference is not arbitrary; it's a function of where Rosh Hashanah landed.
The yahrzeit is the Hebrew anniversary of a death, observed with kaddish and a memorial candle. The math is mostly trivial, but four edge cases trip up naive implementations:
We codify the standard Shulchan Aruch rulings, most modern siddurim use the same. If your community follows a stricter custom (both Adars in leap years, for instance), the tool surfaces the canonical date and you can adjust manually.
The Torah is read on a one-year cycle of 54 parashiyot, but the Hebrew year only fits 50 to 55 Shabbatot depending on length. Several pairs combine in non-leap years to make the math work: Vayakhel and Pekudei, Tazria and Metzora, Acharei Mot and Kedoshim, Behar and Bechukotai, Chukat and Balak, Mattot and Masei, Nitzavim and Vayelech. In leap years (13 months), most pairs split apart again. Festival Shabbats (Pesach, Shavuot, Sukkot) substitute their own readings, so the cycle has to absorb interruptions too. The tool picks the dominant pattern; if you need the exact reading for a festival week, cross-check with your local synagogue calendar.
We're working on candle-lighting and Havdalah times. That needs a sunset calculator parameterised by location and the various community customs (18 / 22 / 40 minutes before sundown). Until then, this tool stays focused on date conversion, yahrzeit, and parashat.