-Later authorities invented the concept of "halachic" hours.
-The Levush invented the procedure of measuring a day from sunrise to sunset.
There are two issues that we will address here. The first is the length of an hour - whether it is 60 standard minutes or one twelfth of the daylight hours. The second is the definition of day - whether it is from dawn until dusk or sunrise until sunset. Surprisingly, there are very few sources that discuss this explicitly. However, as we shall see, there is much that was implicitly assumed that we can infer.
Regarding the length of an hour, the only medieval source we have that discusses this is the Rambam in his commentary to the Mishna in Berachot 1:3 (1:5 in R' Yosef Kaffih's edition). There, he says that an hour in halachic terms is one twelfth of the daylight hours. Therefore, during the summer "hours" are longer than in the winter. Similarly, the length of an hour varies by latitude as well. There are no contrary opinions throughout the medieval halachic literature.
There is good reason for this lack of dissent. The Gemara in Berachot 26b says that Mincha Gedola, the first time one can pray the afternoon service of Mincha, is six and a half hours into the day. However, the last time to pray the morning service of Shacharit is mid-day. If the six and a half hours were of standard minutes then there would be times and places where the time for Mincha overlaps the time for Shacharit. For example, on June 23, 2002 dawn (based on the sun being 16 degrees below the horizon) in New York will be at 2:36 am. Therefore, the earliest time for Mincha using standard hours will be 9:06 am (sunrise will be at 4:25 am so even counting from then yields 10:55 am). Anyone familiar with the discussions of the Gemara there in Berachot knows that the times for prayer cannot overlap. In the language of the Gemara, that is "two that contradict". It cannot be both the time for the morning prayer and the afternoon prayer. Therefore, we are forced to say that, at least regarding prayer, hours must be calculated based on the length of the day. On long days, such as June 23, 2002, "halachic" hours are longer than 60 standard minutes so that the time for Mincha will be in the afternoon (starting at 12:36 pm) and not at nine o'clock in the morning.
Now that we have established that everyone has to argue that there is a concept of "halachic" hours and that the times of the day regarding prayer are determined based on them, it seems that the burden of proof rests with those who want to claim that there is a parallel system of determining times for mitzvot based on standard hours. We know that times for prayer are determined by "halachic" hours. It seems quite a stretch to say that times for reciting Shema are determined by standard hours. From where do we see that any one opinion believes that there are two separate and very different ways to measure the day?
The first to question the propriety of "halachic" hours for Shema and implicitly argue that there are two scales of hours was the Pnei Yehoshua. After him, the Mishkenot Yaakov also suggested this. Both of them, however, did not believe that their arguments were strong enough to override centuries of halachic agreement. Their humility was well-placed because R' Moshe Feinstein (Igrot Moshe, Orach Chaim 2:20) later refuted all of their arguments.
For example, the Mishna (9b) says that until three hours into the day is still considered waking times and therefore the time for the morning Shema because princes sleep that late. The Pnei Yehoshua and Mishkenot Yaakov argued that the amount of time that princes need to slep does not vary based on the length of the day. They sleep a certain amount regardless of the time of the eyar. R' Moshe Feinstein suggested that maybe their sleeping patterns did change based on the length of the day. If on an average day princes sleep three hours into the day - a quarter of the daylight time - that might be because they do not want to waste more than a quarter of the day. On a shorter day, three standard hours might be one third or one half of the day! There is a very good reason to believe that princes varied their sleeping patterns based on the length of the day. If they did not, they would sometimes lose half their day.
Since it is established that there must be halachic hours in regard to prayer, and we have no authority until the 18th century even suggest that standard hours have a place in halacha, those that wish to promote standard hours need to bring strong proof of their claim that halacha follows both "halachic" and standard hours. They have not and cannot do so because there is no strong proof for this theory.
The only medieval authority to speak openly about the boundaries of an halachic day is the Trumat Hadeshen (1) who says that the day begins with dawn and ends with the appearance of stars. One takes the amount of time between these two points and divides by twelve to calculate an halachic hour. However, the inquiring student cannot stop there. There are many hints about this matter implicit in the discussions of the commentators and the student must analyze those as well to fully understand this topic.
Let us return to the Gemara in Berachot 26b. In the Mishna upon which this passage is based, there is a dispute between R' Yehuda and the rabbis. According to R' Yehuda, Mincha can be prayed until Plag Hamincha. After that, it is time for Maariv. According to the rabbis, Mincha can be prayed until night. There is a dispute among commentators whether "until night" means until sunset or until the stars come out. Rabbeinu Yonah, for example, understands it to mean that Mincha can be prayed until sunset after which it is time for Maariv. The Gemara then says that Plag Hamincha is eleven and three quarter hours into the day.
If we were to calculate hours from dawn until the appearance of stars, then on most days of the year Plag Hamincha would be before sunset. However, on some days the times would reverse and Plag Hamincha would be after sunset. This is clearly impossible because, as the Gemara tells us, R' Yehuda selected Plag Hamincha as the ending point for Mincha because the daily afternoon sacrifice may be brought until then. But is it possible for Plag Hamincha to be at night, according to those who define night as sunset, thereby allowing the afternoon sacrifice to be brought at night? Certainly not.
Rather, according to those who place the beginning of night at sunset, the day is measured from sunrise to sunset. This time is divided by twelve to give us the length of an halachic hour. Using this method, none of the times ever reverse themselves.
It is clear from the above that those, such as the Geonim, who define day as beginning at sunrise and ending at sunset calculate "halachic" hours based on these endpoints. Contrary to the claim of some, this is not a recent innovation. Rather, this was how many of the classical authorities must have calculated times in order to avoid the inevitable confusing situations that would arise every single year. For more information, see Minchat Yitzchak 4:53, Jewish Chrononomy by R' Yehuda (Leo) Levi (Hebrew section, p. 21), and R' Israel M. Levinger's article in Jeschurun vol. 9 (1932).
But how, can it be asked, can anyone measure the day starting with sunrise when the Mishna in Megilla 20a says that a mitzvah designated for the day that is performed after dawn but before sunrise is valid? Clearly, day beings with dawn and not sunrise. The answer is that this matter is much more complicated than this Mishna implies. The Gemara in Berachot reads as follows:It is taught (Tosefta 1:2): R' Shimon ben Yachai said, "There are times that one recites Shema twice at night - once before dawn and once after dawn - and one fulfills the obligation [of reciting Shema] for both day and night." This is in itself difficult. It says that there are times that one recites Shema at night. Evidently, after dawn is still night. It then says that one fulfills the obligation for both day and night implying that after dawn is day. No, really after dawn is night but it was called day [regarding Shema] because there are some people who are already awake at that time.
This Gemara clearly states, based on the Tosefta, that the time between dawn and sunrise is night. The contradiction between this Gemara and the Mishna in Megilla is explained brilliantly and eloquently by R' Yosef Dov Halevy Soloveitchik in his Shiurim Lezecher Abba Mori vol. 1 ch. 5. R' Soloveitchik explains that there are two approaches in the Rishonim to explain this apparent contradiction. One is that day begins at some point between dawn and sunrise but we have no way of determining when that time is (similarly, night begins at some indeterminable point between sunset and the appearance of stars). Therefore, we treat this in-between time as a matter of doubt. The second approach is that the in-between time from dawn to sunrise is, paradoxically, both night and day. In certain respects it is night and in others it is day (the same can be said for the time between sunset and the appearance of stars).
If day begins at some point between dawn and sunrise - or paradoxically at both dawn and sunrise - then from when do we begin measuring the length of a day in order to calculate "halachic" hours? Arguments can be made for either time which is why the Rishonim disagreed about this.
In summary, there must be a concept of "halachic" hours in regard to times of prayer and there is no evidence that standard hours have any halachic standing. The Rishonim disagreed over whether the day is measured from dawn until the appearance of stars or from sunrise to sunset. While they do not say this explicitly, it can be inferred from other statements of theirs. And finally, this disagreement is based on the general uncertainty as to how to classify the twilight hours in which day and night seem to overlap.
Contributor(s): Gil Student
Last revised: 1/22/02
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