There are multiple traditions for Havdalah times. Hebcal gives you the option to specify whether you want tzeit hakochavim (sun 8.5 degrees below horizon, a default that works well in most locations on the planet) or a fixed number of minutes after sundown.

Some use 42 minutes after sunset for 3 small stars, 50 minutes for 3 medium stars, or 72 minutes for Rabbeinu Tam. You can choose any time you want. 

Hi Tzipora and Yaakov,

Thanks again for your patience and feedback.

Another update: after some additional research, we've come to the conclusion that the sunset algorithm we were using in the new version of Hebcal wasn't accurate enough. As of yesterday, we have swapped out the sunset engine for a version that matches what we previously published on Hebcal.com and most other sources (including OU).

Some of the Hebcal event feeds are cached up to 1 week, so subscriptions on Google Calendar, iPhone, etc might not refresh until next Sunday August 23.

Another update: after a bunch of research, we've come to the conclusion that the sunset algorithm we were using in the JavaScript version of Hebcal wasn't accurate enough. As of today, we have swapped it out for a version that although less-commonly used in the JS world, seems to match both the previous C version and most other sources.

Some of the Hebcal event feeds are cached up to 1 week, so subscriptions on Google Calendar, iPhone, etc might not refresh until next Sunday.

https://www.hebcal.com/shabbat?geonameid=5110302&M=off&m=72

Shabbat Times Brooklyn, New York, USA

• Rosh Chodesh Elul occurs on Thursday, 20 August 2020
• Rosh Chodesh Elul occurs on Friday, 21 August 2020
• Candle lighting: 7:26pm on Friday, 21 August 2020
• This week's Torah portion is Parashat Shoftim
• Havdalah (72 min): 8:55pm on Saturday, 22 August 2020

./hebcal -c --latitude 40,39 --longitude 73,56 --timezone America/New_York -m 72 | grep --context=2 '8/22/2020'

8/21/2020 Rosh Chodesh Elul

8/21/2020 Candle lighting: 7:26

8/22/2020 Havdalah (72 min): 8:55

8/28/2020 Candle lighting: 7:15

8/29/2020 Havdalah (72 min): 8:44

Thanks so much for the suggestion. No official Android app currently but we hope to make one in the coming year.

In the meantime, you can export Hebcal calendar events to Googld Calendar and then your Android device will see the events.

Update: we've ported the "round Havdalah times up to nearest minute" feature back to C. It's available in hebcal 4.21 and later.

./hebcal --version

Hebcal version 4.21

./hebcal -c --latitude 40,39 --longitude 73,56 --timezone America/New_York -m 72 | grep --context=2 '8/1/2020'

7/30/2020 Tish'a B'Av

7/31/2020 Candle lighting: 7:53

8/1/2020 Shabbat Nachamu

8/1/2020 Havdalah (72 min): 9:23

8/5/2020 Tu B'Av

8/7/2020 Candle lighting: 7:45

Hi, thanks for your patience!

We've finished our website upgrades and now the candle-lighting times are consistent across the website and the downloads/subscriptions in Google Calendar and other calendar apps that consume hebcal.com feeds. Calendar apps like Google or the iPhone tend to refresh calendar subscriptions approximately once a week, and it's now been long enough since we updated our servers that all calendar subscription feeds should be fully refreshed.

Thanks again for using Hebcal!

Hi, thanks for using Hebcal.

One of the features of the new website is that it offers a radio button for Havdalah with two choices - tzeit or fixed minutes. The new default is Tzeit HaKochavim (solar depression of 8.5 degrees) vs. a fixed number of minutes (e.g. 72) after sunset, because it works more consistently across the globe.

Tzeit doesn't apply here, because it looks like in this case you're specifically choosing 72 minutes.

There are 3 things that could account for 1-2 minute differences in candle lighting and Havdalah times:

1. slightly different NOAA sunset calculators - the one we're using on the website now is implemented in JS. It was previously implemented in C. Both use double-precision floating point arithmetic, but there are so many constants and opportunities to round/truncate that there could be slight differences in the resulting number.

2. In JS, we truncate candle-lighting (Friday) times down to the nearest minute, and round Havdalah times up to the nearest minute. The idea here is that it's better to list candle-lighting time as 30 seconds earlier than strictly necessary, and for Havdalah it's better to wait an additional 30 seconds to end Shabbat/yontiff. So if the exact candle lighting time from the sunset engine (including seconds) was at 20:02:31 or even 20:02:59, we have always returned candle-lighting at 20:02 in both C and JavaScript. However, in JS we're operating a little differently for Havdalah times only. If the Havdalah calculation comes back as 21:17:29, JS will display 21:17, but if it were 21:17:30 through 21:17:59 we display 21:18. In the C version, we would display 21:17 for Havdalah even if the engine returned 21:17:59. Should we consider this a bug in the C version and backport the rounding feature to C? It's a 1- or 2-line code change.

3. Lastly, when comparing Hebcal to other sources like OU and Chabbad, most of the differences are explained by slightly different latitude/longitude definitions for a given city. Since 2013, Hebcal.com has been using lat/long definitions from GeoNames.org, which is available under a Creative Commons license. For the USA, we purchase a commercial ZIP code database from zip-codes.com.

In this particular case, it's likely that 1 minute of the 2-minute difference is accounted for reason #1, and the other minute is accounted for by reason #2.

To make a change to a Yahrzeit + Anniversary calendar calendar, delete or unsubscribe from the calendar. Return to Hebcal.com and re-enter in all of the event details, then download again. Hebcal does not yet support editing event dates.

https://www.hebcal.com/home/632/how-to-make-changes-to-a-yahrzeit-anniversary-calendar

Thank you for the bug report. The error has been corrected and now Jerusalem candle lighting times are correctly listed as 40 minutes before sundown. Shabbat shalom!