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Peninei Halakha > Zemanim > 7 - The Laws of the Minor Fasts > 3 – The Duration of the Minor Fasts

3 – The Duration of the Minor Fasts

The minor fasts last from daybreak (alot hashachar) to the emergence of the stars (tzait ha-kochavim). Alot hashachar is when the first light begins to appear in the east. Tzait ha-kochavim is when three medium-sized stars are visible in the sky.  There are different opinions as to when exactly alot hashachar occurs – either when the first light begins to appear in the east (when the sun is 17.5 degrees below the horizon) or a short time later, when the eastern sky is illuminated (when the sun is 16.1 degrees below the horizon).

There are also two major opinions regarding tzait hakochavim.  It occurs either when experts and those with excellent eyesight can see three stars (when the sun is 4.8 degrees below the horizon) or when regular people can see three stars (when the sun is 6.2 degrees below the horizon).

There is a common mistake that people make regarding this issue.  They think that there is a set interval between alot hashachar and sunrise and between sunset and tzait hakochavim, which is not true.  Rather, these intervals depend on the time of year and the place.  Therefore, one should use a precise calendar.[4]

According to the letter of the law, we should follow the more lenient opinion, because these fasts are Rabbinic enactments.  However, it is best to act strictly.  Since we are already fasting all day long, it is preferable to add a few extra minutes in order to fulfill our obligation according to all opinions.

When the Tenth of Tevet falls out on a Friday, one must fast until after tzait hakochavim, even though Shabbat has already begun by then (SA 249:4).

One who flies from America to Israel will fast less time, because he is flying in the opposite direction of the sun.  Every hour in flight shortens the fast by more than half an hour.  If he flies from Israel to America, he will fast longer, because he is flying in the same direction as the sun.  Every hour of flying adds more than half an hour to his fast.  The rule is that the fast starts at alot hashachar and ends at tzait hakochavim, according to the place in which one finds himself at that time (Iggrot Moshe, OC 3:96).

[4]. Regarding alot hashachar, see Peninei Halachah, Prayer, chap. 11, notes 1 and 10.  Regarding tzait hakochavim, see ibid. 25:5, note 3.  [I will give some examples] in order to give the reader an idea [of the differences]:  According to the 16.1° measurement, the interval between alot hashachar and sunrise in Eretz Yisrael on Tzom Gedalyah is around 73 minutes, while it is around 86 minutes on the Seventeeth of Tammuz.  According to the 17.5° measurement, it’s around 80 minutes on Tzom Gedalyah, and around 94 minutes on the Seventeenth of Tammuz.  I wrote “around” because the solar-calendar day on which the Hebrew date falls changes from year to year and this change can make a difference of up to two minutes.  In Israel’s coastal plain, the sun rises later, because the mountains [in the east hide the sun longer].  Therefore, the interval [between alot hashachar and sunrise] increases by about five minutes.  The interval between sunset and tzait hakochavim also fluctuates according to the time of year, but the difference is smaller.  There is also a considerable difference between the mountains and the plains.  According to the earlier measurement (4.8°), the interval [between sunset and tzait] in Jerusalem on Tzom Gedalyah can be as short as 14 minutes.  And according to the later measurement (6.2°), the interval in the coastal plain on the Seventeeth of Tammuz can be as long as 29.5 minutes.  This is why one must use a precise calendar.  In the footnotes cited above from Peninei Halachah, Prayer, I explain the issue thoroughly.

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The Laws of Shabbat (1+2) - Yocheved Cohen
The Laws of Prayer - Atira Ote
The Laws of Women’s Prayer - Atira Ote
The Laws of Pesach - Joshua Wertheimer
The Laws of Zemanim - Moshe Lichtman

Editor: Nechama Unterman