Every yahrzeit record follows one calendar or the other. This is the single most consequential choice on the record, so it is worth understanding properly.
The two options
Hebrew calendar. The anniversary falls on the same Hebrew date every year: 12 Cheshvan, every year, forever. Because the Hebrew and secular calendars do not line up, the secular date moves by roughly eleven days each year, sometimes jumping forward by about nineteen when a leap month is added.
Secular calendar. The anniversary falls on the same secular date every year: 4 November, every year.
Traditional practice observes the Hebrew date. Many families, particularly those less connected to the traditional calendar, think of the secular one. Both are supported because both are real preferences, and the right answer is whatever that family wants.
Why the distinction matters mechanically
A record set to the Hebrew calendar has its date recalculated every year. The system does not store “next year it is 22 October” and reuse it. It asks the Hebrew calendar afresh each time.
This matters because a stored secular date goes stale within a year. If the system trusted it, a Hebrew-calendar yahrzeit would send reminders correctly once and then drift further off every year afterwards. It does not, because it recomputes.
This is also why you cannot fix a Hebrew-calendar yahrzeit by editing its secular date. The secular date is worked out from the Hebrew one. Edit the Hebrew day and month instead.
Entering a date
You can type either one. If you enter a secular date, the matching Hebrew date is worked out and shown to you as you type, so you can check it before saving.
This is genuinely useful when a family gives you a date from a death certificate but wants the Hebrew observance. Type what they gave you, read back the Hebrew date, and confirm it with them.
Sunset
Worth knowing, and worth asking families about: the Hebrew day begins at sunset. Someone who died on the evening of 3 November, after sunset, died on the Hebrew date belonging to 4 November.
The system cannot know what time of day a death occurred. If a family is precise about the Hebrew date they observe, enter the Hebrew date directly rather than deriving it from the secular one.
When a family gives you a date, ask which one they observe. A minute of conversation now prevents a reminder arriving on the wrong day for the next twenty years.
Changing the calendar later
You can change a record from one calendar to the other at any time by editing it. The next observance is recalculated straight away, and the change is reflected in the list.
Leap years
Some Hebrew years have a thirteenth month, which raises a specific question for anyone who died in Adar. See Leap years and Adar. 