By default we follow Chabad zmanim standards. The time for end of Shabbat and Yom Tov is shown according to the Alter Rebbe. On weekdays, however, we use the universal standard for nightfall of three medium stars, also known as the GR"A (Vilna Gaon). The Zmanim page will list both times on Shabbat and Yom Tov.
The Zmanim page lets you pick which halachic opinion to use for calculating the daytime hours (sha'ah zmanit). This choice affects most daytime zmanim: latest time for Shema, latest time for Shacharit, Mincha Gedola, Mincha Ketana, Plag HaMincha, and the end of Shabbat. Three general opinions are available:
Alter Rebbe (default) โ Follows R' Shneur Zalman of Liadi in his Siddur and Shulchan Aruch HaRav. Halachic hours are measured from the amiti (astronomical) sunrise to amiti sunset โ the moment the geometric center of the sun's disk crosses the horizon, ignoring refraction. End of Shabbat is set to when the sky darkens to 8.5ยฐ below the horizon. This is the standard for the Chabad community.
GR"A (Vilna Gaon) โ Halachic hours are measured from visible sunrise (when the sun's upper edge first appears) to visible sunset. End of Shabbat is set to when three medium-sized stars are visible, approximately 6ยฐ below the horizon. This is the majority opinion followed by most Ashkenazi and Sephardi communities. Source: Biur HaGr"a OC 459:2.
Magen Avraham โ Halachic hours are measured from dawn (72 minutes before sunrise, or when the sun is 16.1ยฐ below the horizon) to nightfall (72 minutes after sunset). Because the "day" is longer, halachic hours are longer, and every daytime zman falls earlier than with the GR"A. Some communities follow this stringently for Shema. At very high latitudes where the sun never reaches 16.1ยฐ below the horizon, halachic hours are computed from halachic midnight instead โ see Magen Avraham at high latitudes.
Note: Magen Avraham's version of the 72-minute nightfall is used only for calculating the halachic hour and the parts of the day; it is not used for any other halachic purpose.
Times are computed from your geographic location's astronomical events. Angles given below refer to the sun's depression below the horizon.
Visible sunrise (hanetz hachama) โ The moment the top of the sun first appears above the horizon: sun's upper edge at โ0.833ยฐ (accounting for average atmospheric refraction and the sun's semi-diameter).
Visible sunset (shkiat hachama) โ Same 0.833ยฐ threshold at the end of the day: sun's upper edge disappearing on the western horizon.
Amiti sunrise / amiti sunset (Baal HaTanya) โ The astronomical event: the geometric center of the sun's disk at โ1.583ยฐ, i.e., disregarding refraction and taking the true horizon. This is what the Alter Rebbe treats as sunrise/sunset for the purpose of the halachic day. Source: Seder Hachnasat Shabbat, Siddur Torah Ohr.
A halachic hour is one-twelfth of the halachic day. What counts as the "day" depends on the opinion followed:
The point at which the eastern sky begins to lighten. The site supports several opinions:
The point at which one can distinguish the blue thread of the tzitzit from the white. This is the earliest time to put on talit and tefillin.
The end of the third halachic hour from the start of the day (per the selected opinion). Source: Mishna Berachot 1:2, per the ruling of R' Yehoshua that we follow; Shulchan Aruch HaRav OC 58:3.
The end of the fourth halachic hour. Source: Berachot 26a โ up to four hours the tefilla is le-chatchila.
Chatzot hayom (noon) โ the midpoint between sunrise and sunset. Chatzot halayla (midnight) โ 12 halachic hours after noon, i.e., the midpoint between sunset and the following sunrise.
6.5 halachic hours from the start of the day. The earliest time one may pray Mincha.
9.5 halachic hours from the start of the day. Preferred earliest time for Mincha le-chatchila.
10.75 halachic hours from the start of the day. The earliest time one may accept Shabbat or daven Ma'ariv (per certain opinions).
Visible sunset โ the sun's upper edge disappearing on the western horizon (โ0.833ยฐ). This begins bein hashmashot, the disputed period between day and night.
The end of bein hashmashot โ the halachic transition from day to night. Several opinions:
Nightfall with three small stars, 36 minutes at โ8.5ยฐ. This is the same for all major opinions. Source: Shulchan Aruch OC 293:2. When the Rabbeinu Tam row is enabled, it appears alongside as a stringent alternative. Rabbeinu Tam nightfall might not be displayed in high latitudes where it occurs before the time of three small stars.
At high enough latitudes (roughly above 50ยฐ in the summer/winter extremes) the sun never dips 16.1ยฐ below the horizon, so the Magen Avraham dawn does not occur. When this happens, the site sets the halachic hour to two clock hours (equivalent to treating the halachic day as 24 hours long) and reckons all daytime zmanim from halachic midnight. Times computed this way are marked with an asterisk (*) and carry a footnote advising to consult a competent rav before relying on them.
These reference rows are hidden by default and can be turned on in the gear menu:
The halachic calculation library powering this site is written in Java and is open source on GitHub. A companion C library for the Hebrew calendar arithmetic is also available on GitHub.
Sun times are computed without elevation adjustment, which is the standard approach for halachic purposes. The underlying API does accept an elevation value for those who know what they are doing.
Location search and geocoding use the Google Places API.
Questions or feedback? Email support@hebrewcalendar.net.
© Isaac Mushinsky, 1998–2026