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The hour has a special meaning in Jewish law. "The third hour of the day" doesn't mean 3:00 a.m., or three sixty-minute hours after sunrise. Rather, an hour in halacha is calculated by taking the total time of daylight of a particular day, from sunrise until sunset,1 and dividing it into twelve equal parts. A halachic hour is thus known as a sha'ah zemanit, or proportional hour, and varies by the season and even by the day.

For example, on a day when the sun rises at 5 a.m. and sets at 7:30 p.m., one sha'ah zemanit, or proportional hour, will be 72.5 minutes long. The third hour of the day will come to a close at 8:37:30 a.m.

This information is important because many observances in Jewish law are performed at specific times during the day. The calculation of these halachic times, known as zmanim ("times"), depends on the length of the daylight hours in that locale.

For more information regarding the various halachic times of the day, as well as some of their associated mitzvot, see About Zmanim.

To find out the halachic times for any location, see Zmanim-Halachic Times.

Footnotes
1.

According the other opinions, from dawn ("alot hashachar") until three stars appear in the sky ("tzeit hakochavim").

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Vee May 20, 2017

What is counted as the third hour of the day in Israel?
Thank you Reply

Eliezer Zalmanov for Chabad.org May 21, 2017
in response to Vee:

It varies from day to day. See chabad.org/times for the exact time for any given day at a specific location. Reply

Brendan Moodley South Africa May 9, 2017

Thank you. Reply

Yehuda Shurpin for Chabad.org March 6, 2017

Re:Ebed-melek The article is referring to when the third hour of the day comes to a close, not when it starts. So while it is true that the third hour would start only 145 and not 217.5 minutes later, it does indeed end 8:37:30 a.m (presuming of course that the day started at 5:00am and ends 7:30pm). Reply

Ebed-melek Chicago March 3, 2017

If an hour is calculated to be 72.5 minutes long, why wouldn't the 3rd hour be 145 minutes later as opposed to 217.5 minutes later? In other words, if the sun rose @ 5am,why wouldn't the 1st hour be 5am-6:12:30am? Or is there a zero(th) hour? Reply

samuel india May 11, 2016

hours calculation pls. let me know how the hours are calculated according to the jewish culture Reply

Ben Zulu Empangeni December 29, 2015

This is very interesting Reply

Shaul Wolf July 19, 2014

Re: Jewish calendar The Jewish calendar follows the moon cycle, a year constituting 12 full moon cycles, which takes 354 days. The number 5774 represents the number of such years that have passed since the beginning of creation. Reply

Henry Martin USA May 18, 2017
in response to Shaul Wolf:

Except when there are 13 cycles. The year begins at the first new moon after the first barley is harvested. It has, however, been standardized in a 19 month cycle. Reply

Ron United States of America July 17, 2014

What event marks the beginning of the Jewish calendar system? I have heard that it is the creation of the world, which is taken to be 5774 years ago, I suppose. Did Adam and Eve pass on a calendar similar to the Jewish calendar, using as year one the time from their creation to their first birthday? How is all of this traced back to the beginning? Why is this year called 5774? Reply

Menachem Posner January 13, 2014

RE: correspondence between Jewish and Roman calendar The Jewish day begins at nightfall and the secular day begins at midnight. Since there is the (approximately) six hour lag, technically every secular day corresponds to two Jewish days. However, I do not see how it can span any more than that. Reply

Deborah Jurkowitz January 11, 2014

correspondence between Jewish and Roman calendar Is it possible for a given day in the Gregorian/Western calendar to span two days or more in the Jewish calendar? If so, why? Thank you. Reply

Winston Shaer November 18, 2013

24 hours in the day How was the determination made that the day should be divided into 12 and the night into 12 it could have been 8, or 9, or any other number? Why 12? Why 60 minutes seconds?

I have read that the Egyptians used the joints of the fingers excluding the thumb, that there is an "earlier" Kabbalistic reason but am unable to find an English source and clear explanation. Reply

James New Zealand March 30, 2013

Is the first day of the month a holiday. Also is this day not included in the first week which would make the Sabbath day the Eighth Day Reply

Rabbi Menachem Posner August 6, 2012

To Anonymous, Mesquite, TX You are on the ball. When calculating nighttime hours, we do so by dividing the time from nightfall to dawn into 12 parts. And when we calculate the daytime hours, we do so by dividing the daylight into 12 parts. This means that most times of the years the day hours and night hours are different lengths. Reply

Anonymous mesquite, tx/usa August 5, 2012

If a day starts at evening, should not daylight of a particular day be calculated by taking the time of daylight from sunset to sunrise? Reply

Anonymous Springfield, MO USA May 27, 2012

proportional hour what a concept! exciting new information. Reply

Anonymous phila, pa September 14, 2009

The information that you have posted is very helpful to me in teaching about the keeping of the Jewish Holidays in the furture Reply

Since Biblical times the months and years of the Jewish calendar have been established by the cycles of the moon and the sun. Torah law prescribes that the months follow closely the course of the moon, from its birth each month to the next New Moon.
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