When Shabbat ends: nightfall, 8.5 degrees and Rabbeinu Tam
The start of Shabbat is set by a moment that is easy to see: the sun sets. The end is more complicated, because it depends on the stars. Here is the explanation.
What the Talmud says
The Talmud in tractate Shabbat, pages 34 and 35, describes the period between sunset and full darkness as "bein hashmashos." It is a time of doubt, when it is not clear whether it is still day or already night. Shabbat ends when night has certainly arrived, and the sign is stars: one star is still day, two stars are doubt, and three medium stars mean night.
The trouble is that not everyone can see stars. Clouds and city lights hide the sky. So a measured standard was needed that does not depend on eyesight, and the halachic authorities tried to translate the Talmud's description into a fixed time.
Two main approaches
- The approach of the Geonim: nightfall comes when the sun is a few degrees below the horizon. Calendars use values between about 7 and 8.5 degrees. This site uses 8.5 degrees, which is a relatively stringent value.
- The approach of Rabbeinu Tam: 72 minutes after sunset. He bases this on a discussion in the Talmud in tractate Pesachim, page 94, about the time it takes to walk four mil, and in his view a mil is 18 minutes. Some communities and chassidic groups have followed this for generations.
According to Rabbeinu Tam, Shabbat ends later. Someone who follows this waits another few dozen minutes, which is why the site shows both times side by side.
What a degree below the horizon means
To define darkness precisely, we measure the height of the sun in degrees. When the center of the sun is on the horizon line, that is sunset, and when it is 8.5 degrees below, the sky is dark enough for medium stars to be seen on a clear night. This value is common in calendars, and the difference between it and nearby values is usually a minute or two.
Why the time varies by place and season
How fast the sun drops below the horizon depends on latitude and season. Near the equator the sun descends almost straight down, and darkness arrives quickly. The farther north you go, the more slanted the sun's path, and the transition to night is slower. In midsummer in northern Europe or Canada, the gap between sunset and nightfall can reach an hour or more.
In Israel, and in New York in the fall, the end of Shabbat at 8.5 degrees is about 35 to 40 minutes after sunset. In summer, in a northern city such as New York, the number grows. So you cannot apply one fixed number of minutes everywhere and in every season, and it is best to rely on the calculation.
The far north in summer
In very northern regions, roughly above 58 degrees latitude, the summer sun never drops 8.5 degrees below the horizon. Night never reaches full darkness, so nightfall cannot be calculated by this method. This happens, for example, in parts of Scandinavia and northern Russia in the weeks around the longest day. In such a place the calculator may not show a time.
For these circumstances the halachic authorities gave special instructions, and communities follow the custom set by the local rabbi. There is no single answer for everyone, and if you live in or visit such a place, ask a rabbi.
What to do on Motzei Shabbat
- Wait until the time that you follow, shown on the site as the end of Shabbat, or as Rabbeinu Tam if that is your custom.
- Before that time, do not perform work that is forbidden on Shabbat, and do not begin Havdalah.
- If you need to end Shabbat earlier than usual, for example because of travel or an ill person at home, ask a rabbi how to proceed.
The rule is to follow the custom of the place where you are and the custom of your family. If you are unsure, waiting a few more minutes is always safe.
A note of caution
Everything written here is general background. The actual decision belongs to your rabbi, who knows the local custom and the circumstances. We compare our calculation against hebcal.com, but that is no substitute for asking a rabbi.
More guides
- Havdalah step by step: wine, spices, flame and Hamavdil
- Why candle lighting is 18 minutes before sunset, and how this site calculates
- Candle lighting when traveling, in hotels and across time zones