What are the last times one may eat matzo and afikomen the seder night for the year 5770 in Yerusholayim? Can you please explain your calculations and let me know the final times lechatchilo and bedeieved?
Chatzos Seder Night 5770 – Yerusholayim
All times adjusted for Daylight Savings Times
Chatzos on Seder night is 12:44 a.m.
Chatzos lechumra is 12:16 a.m. for someone who already fulfilled his mitzvoh of achilas matzoh earlier. If one did not fulfill achilas matzoh the Seder night, he should try to finish eating a kezayis of matzoh before 12:09 a.m. If this is impossible, it is best to try to finish eating a kezayis before 12:44 a.m. and if that is also impossible then one can eat the matzoh until 5:18 a.m. (( However, if the first kezayis of matzoh was not eaten until after 12:44 a.m. although one still should eat a kezayis, one should not make a berochoh of “al achilas matzoh” anymore. After 5:36 a.m. (alos hashachar), there is no more point in trying to eat a kezayis of matzoh (Biur Halochoh at the beginning of siman 477). ))
The calculation for chatzos is the middle point between honeitz hachamoh and shekioh. At that moment, the sun is directly overhead. The sun forms a right angle from the point of sunrise and sunset. Exactly 12 hours later is chatzos of the night. That is also the midway point between sunset and honeitz hachamoh of the next day.
The chumra calculates the time from sunset until alos hashachar of the next day. Alos hashachar is really the beginning of the day for all matters requiring a halachic day (e.g., shofar, miloh, kerias megilloh, korbanos etc.). Honeitz hachamoh is a safeguard measure and not a true beginning of the day for any halochoh other than davening shacharis. Therefore, it would seem that the appropriate way to calculate chatzos would be to take the time between sunset (shekioh) and alos hashachar, divide by two and add that time to shekioh. (( Rav Shlomo Zalman Auerbach in Minchas Shlomo Vol. 1 (91:15) develops this idea. It is also found in Eshel Avrohom Tinyono 477.
Rav Auerbach wrote a letter to Rav Tukichinski on this subject after Rav Tukichinski firmly stated that chatzos is midway between sunset and honeitz and not between sunset and alos hashachar. Rav Auerbach argued that that is not the case and for matters of de’oreiso one should calculate midway between shekioh and alos and for matters of derabbonon he can calculate the midway point between 13.5 minutes after shekioh until alos hashachar. He quoted the Malbim that chatzos should be calculated as the midway point between tzeis hacochavim until alos hashachar. This letter is found in Minchas Shlomo vol. 2 (58:19). ))
Shekioh for Yerusholayim is exactly at 7:01:00 and alos hashachar on Pesach morning is 5:18:30 (calculating alos hashachar as 16.1° below the horizon, “72 minutes” in degrees). Accordingly, the night is 10 hours 17 minutes 30 seconds long. Half of that is 5 hours and 8 minutes and 45 seconds.
Lechatchila one should try to complete eating a kezayis of matzoh the first night of Pesach before this time to fulfill his de’oreiso responsibility. If a person had a kezayis of matzoh by this time and wishes to have the Afikomen before the stringent interpretation of chatzos, he can consider chatzos 12:16 a.m. ((Afikomen is not a chiyuv de’oreiso and therefore even when being machmir to calculate chatzos as the midpoint between the beginning of night until morning, one does not need to calculate from shekioh, but rather from the earliest point after bein hashemoshos.))
The calculation is as follows:
Shekiah is at 7:01. By adding 13.5 minutes to pass bein hashemoshos, we reach 7:14:30. Alos Hashachar is 5:18:30 a.m.
The difference in time is 10:04; that is considered the whole night. Half of that is 5:02.
We then add the time of half the night to the beginning of the night to reach chatzos.