Zmanim Terms

Many observances in Jewish law are performed at specific times during the day. The calculation of these halakhic times, known as zmanim (Hebrew for "times"), depends on the various astronomical phenomena of the day for the specific locale. Sunrise, sunset, the amount of time between them, and the sun's angular position before rising are all factors that determine the halakhic times and "hours" of the day.

The time-determined mitzvot are listed in the table of Zmanim and include, for example, the earliest time to don tallit and tzitzit, the latest time that one can say the Kriat Shema and the morning prayer, and the interval of time within which one must say the afternoon prayer, and other mitzvot. One also needs to know the time of sunset where one is located in order to determine the times of the beginning of Shabbat and holidays and the definition of "night" in order to determine the time of Havdalah.

Many of these times are dependent on the "sha'ah zmanit," the "proportional hour," a special unit of time that takes into account variations in the length of the day—the "hour" has special meaning in Jewish law. When we say that a certain mitzvah may be performed three hours into the day, this doesn't mean at three o'clock in the morning or three clock hours after sunrise. The precise meaning of the sha'ah zmanit is subject to differences of rabbinic opinion as to its exact definition.

The major zmanim calculations are attributed to two rabbis. Rabbi Avraham "Abaleh" Gombiner (1637–1683) of Kalisz, Poland, wrote his commentary on "Orach Chayim," the section of the Shulchan Aruch that deals with the "Laws of Daily Life and Holiday Behavior," such as the "Laws Concerning Rising in the Morning," the various prayers, special prayers, and mitzvot of the holidays. According to Rabbi Avraham, the "Magen Avraham," the proportional hour is obtained by dividing by twelve the time interval between "alot hashachar," the pre-sunrise event that occurs when the rays of the sun first become evident and the sky begins to lighten, and "tzeit hakochavim," "starshine," defined as that time when three stars of medium brightness become visible in the sky. In this method, if the sky lightens at 5:00 a.m. and the stars appear at 7:30 p.m., a duration of 14.5 clock hours (870 minutes), then dividing by twelve produces the value for the sha'ah zmanit on this date: 72.5 minutes.

This differs from the opinion of Rabbi Eliyahu ben Shlomo Zalman of Vilna (1720–1797), the "Vilna Gaon," who holds that the sha'ah zmanit is defined by dividing by twelve the interval between "hanetz hachamah," sunrise, the moment that the first sliver of the sun itself first becomes visible in the sky, and "shkiat hachamah," sunset, the time that the disk of the sun disappears completely beneath the horizon. Using the above example, sunrise would be about 6:30 a.m. and sunset at 6:40 p.m. and one sha'ah zmanit is almost exactly 60 minutes.

Obviously, the sha'ah zmanit as defined by the Magen Avraham is longer than the unit as defined by the Vilna Gaon. This is significant in determining certain zmanim.

In the tables, the zmanim according to Magen Avraham are shown by M"A. The zmanim as defined by the Vilna Gaon are identified by GR"A.

Below you will find the names of the Times, their meaning and associated mitzvot:

Alot HaShachar:

First-light dawn. Fasts begin at this time. According to the Magen Avraham, the calculation of sha'ot zmaniot begins now.

Earliest Tallit:

The halakhic description of the earliest time to don tallit and tefillin is "when one can recognize a familiar acquaintance." Such a determination, close to daily human experience, occurs when it is light enough for someone to first recognize a familiar acquaintance, someone with whom one has only exchanged greetings, as opposed to a close friend, whom someone would recognize from a variety of non-visual cues, no matter how little the quantity of available light. That time, which one may also read off the face of an ordinary clock, say Chazal, is the earliest time that one may make a brachah. As this is a subjective experience, the time given is approximated to an 11 degree depression of the sun.

HaNetz HaChamah:

Sunrise. The calculation of sha'ot zmaniot begins now according to the Vilna Gaon and most opinions. Those who wish to daven vatikin time their amidah for sunrise.

Kriat Shema:

Three sha'ot zmaniot into the day. Latest time of the day to fulfill the biblical daily requirement to recite the Shema. B'dieved (post facto) one may still recite Shema with its blessings until four sha'ot zmaniot into the day.

Tefillah:

Four sha'ot zmaniot into the day, ideally the latest time for Shacharit, the morning prayer. However, if this time was missed, Shacharit may be recited until midday.

Chatzot:

Midday. B'dieved (post facto) one may recite Shachrit until this time. Half-day fasts end at this time.

Minchah Gedolah:

Half a sha'ah zmanit or 30 minutes after chatzot, whichever is greater. The earliest time one may recite Mincha, the afternoon prayer.

Minchah K'tanah:

Nine-and-a-half proportional hours after sunrise.

Plag HaMinchah:

The last eighth of the day. The earliest one may bring in the Shabbat on Friday afternoon. According to Rabbi Judah, if one recites Mincha before plag haminchah, Ma'ariv (the evening prayer) may be recited any time afterward.

Shkiat HaChamah:

Sunset. The latest time for Mincha, the afternoon prayer. The time following shkiat and before tzeit hakochavim is called bein hashmashot, "twilight." Many laws relate to this period and it can be categorized as either the previous or the next day. The accepted custom is to light Shabbat and festival candles 18 minutes before shkiat. Some communities may have adopted an earlier time as their unique custom as to the time to light candles.

Tzeit HaKochavim:

Nightfall ("Starshine"). Earliest time for Ma'ariv (evening service), according to Rabbi Judah's rabbinic counterparts. Full-day fasts end at this time. Earliest time for reciting the evening Shema and counting the Omer. A woman who has completed her cycle of seven pure days goes to the mikvah after this time. This calculation is for the sun's disk at 5.95 degrees below the horizon. There are several definitions used to determine the time of nightfall; this is the earliest.

7.08° below horizon:

Some communities observe tzeit when the sun is at 7.08 degrees below the horizon.

3 Medium Stars:

One might wonder, since nightfall is usually defined as the appearance of three stars in the sky, why can't one simply look up at the sky and see whether three stars are visible? One reason is that there is no standard for determining how bright the stars must be: bright, medium, or dim (small). But the definition of what constitutes "bright," "medium," or "dim" obscures the issue; additionally, the presence of clouds in the sky will also tend to make this determination difficult. Thus the rabbis had to come up with an estimate for how long to wait. Bright stars are eliminated, and only medium and small stars are considered. The calculation for the time of appearance of three medium stars is when the sun's disk is at 7.5 degrees below the horizon.

3 Small Stars:

Shabbat and festivals end at this time, and work may resume as a weekday. Since one is reluctant to see the holy days end, a stricter calculation of tzait hakochavim is used. Known as "three small stars," it is the criterion for evening and is calculated by the sun's disk at 8.75 degrees below the horizon.

Rabbeinu Tam:

The determination of "night" in halakhah is a topic that is highly complex and controversial. It is understood that the shift from day to night is a process and thus the issue of pinpointing a moment of transition becomes complex; further, much disagreement exists as to the identification of the markers of the process; also, different areas of halakhah may use different definitions. (For example, kodashim may use a different standard; see Tosafot, Zevachim 56a, s.v. minayin, and Chiddushei Chatam Sofer, Sukkah 38a, s.v. mi.).

Before embarking on the discussion of when night occurs we must define the term "mil." A "mil" is a talmudic unit of distance similar to a mile, and is used in many places as a period of time; the amount of time it takes a average person to walk a distance of a mil, according to most poskim, is 18 minutes.

Much of the debate has centered around the resolution of two statements attributed by the Talmud to R. Yehudah. In Shabbat 34b, the period of bein hashmashot (twilight, in between shkiat and tzait hakochavim) is identified by R. Yehudah as three-quarters of a mil. If the time for a typical person to walk one mil is taken as 18 minutes, then it emerges that tzait hakochavim is 13½ minutes after shkiat. However, a different impression comes from Pesachim 94a. There, in a discussion concerning the dimensions of the Earth, R. Yehudah states that in between shkiat and tzait hakochavim there are four mil. Again assuming an 18-minute mil, that would result in a bein hashmashot of 72 minutes; quite different from the first statement.

The resolution of this contradiction is at the root of a major dispute associated on one side with the geonim and the Vilna Gaon (GR"A) and on the other side with Rabbeinu Tam, a grandson of Rashi. According to the first school of thought, of which the geonim (See Responsa Maharam Alashkar, 96, citing R. Sherira Gaon and R. Hai Gaon) and the GR"A (see Biur to Shulchan Arukh, 261:2) represent different versions, the statement in Pesachim is not applicable to the halakhah in these cases. Thus, ¾ of a mil after shkiat is tzait hakochavim, and the time in between is bein hashmashot.

Rabbeinu Tam (see Tosafot, Berakhot 2b, s.v. dilma; Shabbat 35a, s.v. trei; Pesachim 94a, s.v. R. Yehudah), however, resolves the issue differently. In his assessment, there are actually two points called shkiat. The first shkiat takes place when the sun begins to sink beneath the horizon. The second shkiat refers to the point once the sun has already sunk. The four-mil period refers to the time in between the first shkiat and tzait, while the ¾-mil period is the time from the second shkiat until tzait. (In addition, a third opinion exists; see Sefer Yereim, 274.)

Powerful support exists for both sides. On the one hand, the position of the geonim is effectively expressed by the GR"A's statement that Rabbeinu Tam cannot be right because hachush makhchish, "one's senses contradict it": a glance outside the window will verify that it is pitch black long before four mil have passed from the time of shkiat. Indeed, much of k'lal Yisrael have in modern times accepted the position of the geonim.

However, Rabbeinu Tam's position also carries much support, as it is actually the view of many other rishonim as well, up to and including the Shulchan Arukh (Orach Chaim 261:2) and the Rama (see also Magen Avraham, 331:2, and Responsa Chatam Sofer, O.C. 80.). Thus, many are reluctant to not end Shabbat until "Rabbeinu Tam z'man," a practice advocated by R. Moshe Feinstein (Responsa Iggerot Moshe, Orach Chaim IV, 64) and considered normative by communities such as Satmar (see Responsa Divrei Yoel, 18). On the other hand, R. Herschel Schachter and R. Mordechai Willig (see Am Mordechai to Berachot, 2) consider the view of the geonim to be dominant.

Rabbeinu Tam's position may seem to be difficult to defend but consider the following. If one assumes the period of bein hashmashot to be ¾ of a mil, and if that is understood to mean 13½ minutes, it does not seem to be the case that darkness has already descended once that much time has passed since shkiat. The GR"A thus notes that this measurement is not meant to apply to every part of the world, but only to Israel and Babylonia (which share the same latitude). However, R. Yechiel Michel Tukichinsky, in his Bein HaSh'mashot, notes that even in Jersualem, stars are not visible until about 22 minutes after shkiat. R. Yehudah Levi (Z'manei HaYom B'Halakhah) observes that there is a difference in this area between the trained eye and the untrained eye. In Jerusalem (during the month of Nissan) an expert can discern three stars after about 15 minutes, a time not significantly different from ¾ of a mil.

Identifying the exact moment of "night" has two implications. First, it is the time when the old day is over and the next has begun. Second, it is the time of "night" for the purposes of halakhah. Thus, when bein hashmashot is identified by the gemara (Shabbat 34b) as being a safek (indeterminate situation), the connotation would appear to be that there are two undetermined aspects: whether or not it is night, and whether or not the day has changed.

The Radbaz (Responsa, 1442) brings this understanding into a resolution of an apparent contradiction in the words of the Rambam. In Hilkhot Shabbat (5:4) he writes that due to the indeterminate nature of bein hashmashot, one may not work on Friday night after shkiat. However, in Hilkhot Kiddush HaChodesh (2:9) he rules that despite the fact that sanctifying the new month can only take place during the day, after shkiat is still acceptable within that definition. The Radbaz thus asserts that perhaps the two issues in defining night are independent of each other. Thus, Friday can (possibly) switch over to Shabbat, while still maintaining the character of "day." (For other resolutions to this problem, see Chavatzelet HaSharon al HaTorah, Bereishit, p. 8).

R. Moshe Shternbuch (Moadim U'Zmanim, II, 155, fn. 1) considers the question of those parts of the world where darkness never actually sets in. He suggests that the day changes at whichever point the distance between those places and the sun is the greatest, but that halakhic "night" does not take effect at all. Thus, one living in those areas would be unable to fulfill any mitzvot dependent on night. He does consider, without a conclusion, that k'riat sh'ma might be an exception, as the controlling terminology is not "day" and "night" but rather "lying down" and "rising."

One of the prevailing opinions is based on the view of the Geonim Rabbeinu Sherira, Rabbeinu Hai and Rabbeinu Nissim. This view assumes that the period of bein hashmashot, an astronomical event relating to the definition of "night," begins as soon as the entire disk of the sun drops below the horizon. It also takes into account variations in astronomical phenomena as seen from different parts of the earth. Thus, according to this view, the time interval between shkiat, sunset, and tzait hakochavim, night/starshine will vary at a given location from time to time, and at different locations around the world.

The second opinion is that of Rabbeinu Tam, that the period of bein hashmashot begins later, when light has disappeared from all of the sky except the western horizon. To handle variations in the astronomical phenomena as seen from different parts of the earth, as well as the reasons stated by the Talmud—our lack of familiarity with the categorization of the brightness of stars, as well as the possibility of cloudy skies—Rabbeinu Tam falls back on the estimate provided by the Talmud for the amount of time between sunset and night/starshine as the time estimated for an average person to walk four mil, the total time for that walk estimated to be seventy-two minutes, throughout the year at a given location and at all points on the earth. Thus, according to R. Tam, night occurs 72 minutes after sunset.

Sha'a Zmanit:

The "proportional hour" of this date as described above.