Does one complete fast days derabbanan according to the Gra ,10-20 minutes after sunset? Will this include tisha bav? If someone is makpid a whole year to say kiddush lavanah after 3 days, can he do the same for the month of av?
Answer:
If somebody is makpid to say kiddush levanah after 3 days, he can do so even in the month of Av, and some have the custom of doing so (see Maaseh Rav, and Aruch Hashulchan 551:22). However, the general custom is to wait until Motza’ei Tisha Be’Av.
According to the Gra, nightfall is 13-18 minutes after shekiah (the general custom is not less than 18), and for those who follow this custom it applies even to Tisha Be’Av.
