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Parshas Bo – The Halachic Time of Chatzos

“And it was in the Middle of the Night”
The Halachic Time of Chatzos

In Parshas Bo, In the introduction to the final plague of the Death of the Firstborns, Hashem sets the time of the plague for midnight. Moshe thus informs Pharaoh: “At around midnight (ka-chatzos) I shall go forth in Egypt” (Shemos 11:4).

Chazal (Berachos 3b) note the word ka-chatzos (around midnight), which is used in place of ba-chatzos (at midnight). Why is the inaccurate form used over the precise form? The Gemara explains that Hashem in fact used the precise form of the word, but Moshe changed the word to the imprecise form.

The reason for this change, as the Gemara explains in its conclusion (according to one explanation), is that Moshe was concerned that Pharaoh’s astronomers will miscalculate the time, and will therefore claim: “Moshe is a pretender.”

As we will see later, this episode is used by some authorities to gain a halachic insight into the time of midnight, chatzos. In this article we will try to explain the principles of how the time of midnight—and also the time of midday—are calculated, and show why this calculation is important for many halachic purposes.

The Time of Midday

Before reaching the halachic subject of midnight, it is important to introduce the relatively simple calculation for the time of midday. This time is of great importance for many halachic purposes, including the following:

1) The prohibition of chametz from chatzos on Pesach eve.

2) The beginning of the time for davening Minchah—half-an-hour after chatzos.

3) The prohibition of taking a haircut, entering a bathhouse, and eating a festive meal, before davening Minchah, begins at chatzos.

4) The Shacharis prayer can be prayed up to chatzos, if the proper time was inadvertently missed.

5) It is prohibited to fast up to chatzos on Shabbos/festivals (Magen Avraham 157:6).

6) The prohibition against sitting on a regular chair on Tisha Be’Av ends at chatzos.

The time of chatzos ha-yom is quite simple the time when the sun is in the middle of the sky, in a straight line above one’s head. According to the majority of authorities, this time is easily calculated by finding the midpoint between the time of sunrise (zerichah) and the time of sunset (shekiyah). According to this, the time of midday changes from day to day, depending on the respective times of sunrise and sunset (see Shaarei Teshuvah, Orach Chaim 89:1).

Although this is the opinion of most authorities, it is noteworthy that Rav Moshe Feinstein (Iggros Moshe, Orach Chaim Vol. 2, no. 20) had an original approach to the time of chatzos, arguing that halachic midday is at a fixed time throughout the year. Rather than the time of chatzos, the changing factor is the two halves of the day: sometimes the first half is longer, and sometimes the second. This principle is also stated by the Aruch Ha-Shulchan (Orach Chaim 233:14), who likewise writes that the time of midday is always at the solar noon (12:00 solar time, when the sun crosses the local meridian). This comes to 11:56 am in New York, or 11:37 in Jerusalem.

However, the factual evidence points at a changing time for chatzos, meaning that the time when the sun is “above our heads” changes daily as the midpoint between sunrise and sunset. The great majority of poskim endorse this ruling, and this is the customary time cited by calendars.

The Time of Midnight

The time of midnight—chatzos lailah—is also an important time for halachic purposes, including the following:

1) The mitzvah of eating matzah (Torah) and afikoman (rabbinic) on Seder Night.

2) The nighttime Keriyas Shema, which must be read (rabbinic) before chatzos.

3) Tikkun chatzos, the special prayer over the destruction of the Mikdash, is recited at chatzos.

Determining the time for midnight is more difficult than the time for midday, because by contrast with the day, there is no astronomical indication of its arrival.

The Magen Avraham (1:4) writes, citing from the Zohar (Vayakhel), that the period of the night should always we considered as a twelve-hour period, both in the summer and in the winter. The Machatzis Hashekel explains that this means one should count a period of twelve hours from the time of nightfall (when the stars come out). Midnight is midway into the night—six hours after nightfall. Note that according to this definition, night can actually continue into the morning hours of daylight.

However, poskim do not follow this approach. As the Magen Avraham cites from Shut Shev Yaakov (Vol. 1, no. 1), authorities generally maintain that the time of midnight is defined as the actual “middle of the night,” meaning the halfway point between nightfall (tzeis) and daybreak (alos). This ruling is elucidated by the Tashbatz (Vol. 1, no. 109), the Shulchan Aruch Ha-Rav (1:8), and by many other poskim (see Kaf Hachaim 1:8).

According to the above ruling of Rav Moshe Feinstein, it follows that midnight, just as midday, will always be fixed at twelve hours after halachic midday. Indeed, the Rebbe of Ziditchov is cited (see Kumi Roni, no. 9) as stating that the time of chatzos (night) is always at “twelve o’clock on the watch” (it is possible that like Rav Moshe Feinstein, he meant twelve o’clock solar time, and not Greenwich Mean Time; see also below, where we write that the time of chatzos with regard to tikkun chatzos might be different).

The same conclusion can possibly be reached according to other opinions, who use standard hours for dividing the day, and not halachic hours that vary according to the length of the day. We will not go into this issue, because the great majority of authorities side with the sha’os zemanios (relative hours) of the Ramabam, and determine the time of chatzos accordingly.

The Virtuous Time of Chatzos

The Magen Avraham himself (233:4) notes the apparent contradiction between the above-mentioned teaching of the Zohar, and the basic halachah for determining the time for chatzos.

He responds that concerning the virtuous time of chatzos, which is the appropriate time for tikkun chatzos, we do not consider the astronomical cycles of the day and the night—which do not exist with regard to Hashem—but rather establish the time of chatzos based on a standard twelve-hour night.

However, concerning prayer, which corresponds to the sacrificial service and depends on earthly calculations, we base our times on the actual nightfall and daybreak. This likewise applies for purposes of times for Shabbos and festivals.

It thus emerges, according to the Magen Avraham, that there are two distinct times for midnight (and, perhaps, even for midday): one is the time of midnight for purposes of regular halachah, and another is the time of midnight as a virtuous time, which is the appropriate time for tikkun chatzos.

Calculation of Midnight based on Midday

Based on the above calculation, whereby the time of chatzos is the midpoint between nightfall and daybreak, it follows that there is no necessary correlation between the halachic times of midnight and midday. The time of midnight is the midpoint between the beginning of the night (nightfall) and the start of the day (daybreak)—a time that has no specific connection with the halfway point between sunrise and sunset.

However, some of the poskim mentioned above mention that the time of midnight can be calculated by adding twelve hours to the time of midday: the time of midnight is thus the same as the time of midday. This equivalence is stated by Shut Shev Yaakov (loc. cit.), by the Yad Efraim (1), the Ya’aros Devash (Vol. 1, Derush 15; Vol. 2, Derush 12), the Siddur Ya’avatz, and others.

According to this method, the time of midnight is the midpoint between sunset and sunrise—just as midday is the midpoint between sunrise and sunset. The logic of this is that the time of midnight is thus the astronomical parallel of midday: If at midday the sun is “above our heads,” at midnight the sun is “beneath our legs”—the midpoint of the path of the sun away from the earth.

Yet, there are authorities who note that this method of equivalence should not be used for determining the time of midnight, because this is not the actual “middle of the night.” Rather, the time should be calculated as mentioned above, by finding the halfway point between nightfall and daybreak. If we apply the nightfall of the Geonim (as ruled by the Vilna Gaon and the Ba’al Ha-Tanya), this calculation will yield a far earlier time for midnight than the equivalent of midday.

Thus, in his approbation to Matzos Mitzvah, the author of Pe’as Ha-Shulchan criticizes the custom of relying on the time of midday even for midnight, and writes that one should be stringent (for Torah matters, such as eating matzah) in following the earlier time as calculated above. The Eshel Avraham (Butshatch, 477) is doubtful over which is the true time for midnight: the equivalent of midday, or the midpoint between nightfall and daybreak.

The Chatzos of Eretz Yisrael

Chazal point out (see Yevamos 72a, and Rashi) that the time of chatzos (midnight) is a particularly virtuous time for Torah and for prayer. This is the reason why some are particular to awaken from their sleep at midnight—as King David used to do (Berachos 3b)—for prayer and Torah study (see Tur, Orach Chaim 1).

We have already seen a possible distinction between midnight as a time of virtue, and the regular, halachic definition of midnight. In this spirit, the Chasam Sofer (Toras Moshe, Bo) makes a far-reaching statement concerning the virtuous time of midnight.

On the Gemara (quoted at the outset) of how Moshe Rabbeinu changed Hashem’s precise reference to an approximation of midnight, the Chasam Sofer asks the following question. The Gemara explains that King David could determine the precise time of chatzos by means of placing a harp outdoors, and observing when the harp sounded to the special midnight wind. If so, why could Moshe not use the same method of determination?

[The Gemara actually concludes that Moshe knew the time of midnight, but the first stage of the Gemara implies that Moshe did not use this method.]

The Chasam Sofer replies that when Hashem predetermined the time of the final plague for midnight, the reference was not to midnight in Egypt, but to the midnight of Eretz Yisrael. On account of the slight difference between the times, Moshe could not use the test of the harp.

The principle whereby the true time of midnight—at least with regard to chatzos being a virtuous time for prayer and for Torah study—depends on midnight of the Land of Israel, is also stated by the Mor U-Ketziah (Orach Chaim 1). Moreover, Rav Yaakov Emden elsewhere (344) applies the same idea to the changeover of days: the principle determination of which day of the week at any given time depends on the Land of Israel.

Other poskim, however, do not make any mention of the importance of the Land of Israel in this regard, and the Iggros Moshe (loc. cit.) explicitly rules out this suggestion, explaining that chatzos is calculated for each place according to its local times (see also Shut Even Yekarah, Milu’ei Even 9, who writes that the reason why Moshe was afraid to cite a precise time was because of local variations in the time of midnight across the land of Egypt).


As noted, the principle halachah is that the times of midday and midnight change from day to day—though according to the Iggros Moshe it occurs at a fixed time  of the day.

Based on the standard method of calculation, midday (chatzos ha-yom) is the time when the sun is above our heads, which is the halfway point between sunrise and sunset. The general custom is to use the same time for midnight, and this is the time that generally appears in calendars.

Some are stringent for purposes of Torah law (eating matzah on Pesach, but not for afikoman) to use an earlier time of midnight, which is the midpoint between nightfall (the earlier time of tzeis ha-kochavim) and daybreak.

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