Hebcal uses the algorithm defined in Calendrical Calculations by Edward M. Reingold and Nachum Dershowitz, which accords with Ashkenazic practice.

The customary anniversary date of a death is more complicated and depends also on the character of the year in which the first anniversary occurs. There are several cases:

• If the date of death is Marcheshvan 30, the anniversary in general depends on the first anniversary; if that first anniversary was not Marcheshvan 30, use the day before Kislev 1.
• If the date of death is Kislev 30, the anniversary in general again depends on the first anniversary — if that was not Kislev 30, use the day before Tevet 1.
• If the date of death is Adar II, the anniversary is the same day in the last month of the Hebrew year (Adar or Adar II).
• If the date of death is Adar I 30, the anniversary in a Hebrew year that is not a leap year (in which Adar only has 29 days) is the last day in Shevat.
• In all other cases, use the normal (that is, same month number) anniversary of the date of death.

[Calendrical Calculations p. 113]

https://www.hebcal.com/home/wp-content/uploads/2022/02/spier-pg7.png

Thanks for using Hebcal!

If you'd like to display the Hebrew date in addition to the Gregorian date, please visit https://www.hebcal.com/hebcal and create a customized calendar and check one of these two boxes.

• Show Hebrew date for dates with some event
• Show Hebrew date every day of the year

Hi, thanks for using Hebcal.

If you'd like to delete Hebcal from your macOS calendar, you can follow these instructions:

https://www.hebcal.com/home/78/apple-ical-delete-hebcal-jewish-calendar

Hi Ms. Jackler, thanks for using Hebcal.

We checked our security certificate and we think it's perfectly fine.

https://www.sslshopper.com/ssl-checker.html#hostname=hebcal.com

Can you double-check your web browser and make sure you're running a recent version of Chrome, Safari, Firefox or Edge?

Hi, thanks for using Hebcal's Yahrzeit + Anniversary calendar!

If you visit https://www.hebcal.com/yahrzeit in the same web browser where you earlier created a calendar, you will now see a page that looks like this: 

If you click one of the existing personal calendar links, you can share the URL with someone else.

Please note that sharing the calendar shares both view and edit permissions. They will be able to make changes, including adding new names or deleting existing names. Only share the URL with someone that you trust.

Hi, thanks for using Hebcal.

We're sorry to hear that you're having difficulty with Hebcal yahrzeit calendars and Outlook.

Unfortunately, we aren't able to offer any useful suggestions to fix the problem. We have never seen an issue like this before, and you are the first user to report such a problem.

We can leave this question open in the hopes that someone else will find the solution and post the answer here.

If you return to the https://www.hebcal.com/yahrzeit page from the same web browser you used earlier, you should now see a page that lists your previously created calendars:

Then, click on an existing personal calendar link.

Near the bottom of the page, you'll see a green button that says "Add another name"

Fill out the new row and click the blue "Update Calendar" button at the bottom of the page.

Hi, thanks for using Hebcal.

We regret that we do not currently offer a personalized zmanim service (alot haShachar, mincha ketana, etc).

We do offer candle-lighting and havadalah times for holidays and fast/start end times via https://www.hebcal.com/hebcal

Try this API. This is the best we can offer. Good luck and Shabbat shalom!

https://www.hebcal.com/home/219/hebrew-date-converter-rest-api

if you are not a JavaScript developer, you might consider using our CSV export instructions 

https://www.hebcal.com/home/12/outlook-csv-jewish-holidays