What you need before you calculate
Gather the date of passing as precisely as family records allow. Many calculators ask whether you are entering a Hebrew date (for example 14 Kislev 5781) or a civil date (December 1, 2020). If only a Gregorian date appears on a death certificate, a quality yahrzeit tool converts it using established Hebrew calendar libraries.
Also note your timezone and whether death occurred before or after sunset (bein hashmashot). In borderline cases, the halachic day can shift, which changes the annual Hebrew anniversary downstream.
The core rule: Hebrew anniversary of death
For most Ashkenazi practice, the yahrzeit is observed on the Hebrew calendar date of death each year. That means if someone passed on 7 Sivan, the yahrzeit returns on 7 Sivan annually, mapped to the correct civil day in your local timezone for candle lighting and synagogue attendance.
Automated yahrzeit calculation uses the same rules as Hebrew calendar engines (including leap-year Adar handling). Manual counting on a wall calendar is error-prone; apps and services exist precisely because a one-day mistake is emotionally costly.
Step-by-step yahrzeit calculation
Follow these steps for a reliable annual date:
- Confirm Hebrew or Gregorian input with family and documents
- If Gregorian only, convert the date of death to a Hebrew date once, using a trusted converter
- Apply sunset rules if death was near evening (consult rabbi if unsure)
- Project that Hebrew month and day onto the current Hebrew year
- Convert the resulting Hebrew date back to civil dates for reminders and travel
- Set alerts several days ahead so synagogue, cemetery, and family plans align
Using a yahrzeit calculator vs doing it by hand
Hand calculation teaches the calendar; software prevents silent errors. Yahrzeit Alerts and similar tools store the original date, recompute each year's observance, and send email reminders at offsets you choose (30 days, 7 days, morning-of, and more).
When comparing calculators, check whether they handle Adar I / Adar II in leap years and whether display times respect your timezone. Small differences between websites usually mean different sunset assumptions or civil mapping methods.
If siblings live in different time zones, agree on one reference location for the Hebrew date, usually where the person lived or where burial took place. Document that choice in your family notes so future years do not reopen the debate.
Key takeaways
Start from the most accurate date and time of passing you have, then convert to Hebrew once and reuse that anchor every year.
Software should recompute the civil date annually; you should not manually roll the calendar forward each spring.
- Document Hebrew and civil dates in one place for siblings
- Flag sunset and burial edge cases for rabbinic input
- Verify Adar rules in leap years before the year arrives
- Set multi-day email reminders before travel or synagogue needs