The minyan I’m davening mincha with is delayed, may I wait and daven after shkia? And what do people mean when they talk about an additional 4 minutes after shkia?
By Rabbi Chaim Hillel Raskin, Rov of Anash in Petach Tikvah.
The time period between sunset and the emergence of three medium stars is called bein hashmashos, and it is a doubtful zone between day and night. Its duration is the time it takes to walk ¾ of a mil. Assuming that to walk a mil takes 24 minutes, it is 18 minutes long. (The Alter Rebbe primarily follows this view, but writes to be stringent lechatchila to consider a mil 18 minutes.)
R. Yosei’s opinion in the Gemara is that bein hashmashos itself is very short, but begins immediately after the ¾ mil. Therefore, 2 more minutes are added following the 18 minutes. In addition, the exact shkia is 4 minutes after the sunset that we see. The count only starts then, totaling 24 minutes from the visible sunset.
This formula is based on the sun’s position below the horizon (6°) as seen from Yerushalayim on the spring equinox. The precise amount of time fluctuates according to the location and time of year. The conclusion of Shabbos is always slightly later to factor in tosefes Shabbos.
Mincha ought to be davened before shkia when it is unquestionably daytime. Since, however, bein hashmashos may possibly still be considered day, the Alter Rebbe rules in case of need that it may be davened until tzeis. Since the times for davening are derabanan, we rule leniently in case of doubt. According to minhag Chabad, one would still recite tachnun during bein hashmashos.
Shema is to be recited after it is positively night (and many wait until three small stars, 6.83°, for biblical obligations like shema). The Tzemach Tzedek rules that if one regularly davens maariv after tzeis and the only available minyan is earlier, it is better to daven alone at the right time to properly recite shema with its brachos before Shmoneh Esreh.
If a child is born during bein hashmashos, his bris is counted eight days from the night. (If this occurred at the onset of Shabbos, his bris is postponed until the following Sunday since a bris overrides Shabbos only when it is positively the eighth day.) A child is considered bar or bas mitzva only from the second day when they are certainly of age.
If a person passed away during bein hashmashos, kaddish should preferably be recited on both days. If one wishes to set only one day, he should discuss with his rov which day to choose (if it was at the conclusion of Shabbos, Shabbos is often the preferred choice).
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