According to Shulĥan Arukh (493:1-2), the customs of mourning begin on the first day of the omer and last until the morning of the 34^th. This is based on the tradition that, according to the Gemara, R. Akiva’s students died until pros ha-Atzeret, meaning fifteen days before Shavu’ot. This implies that we must continue mourning until the 34^th day of the omer. However, as with the laws of mourning during shiva (the seven-day mourning period for a close relative), a small part of a day is considered like a whole day. Therefore, just as a mourner may terminate his shiva period after starting to mourn for only a short time at the beginning of the seventh day, since he has effectively completed that day, the same applies to the mourning of the omer period: One need not wait until the end of the 34^th day. Rather, all customs of mourning cease to apply a few moments after daybreak on the morning of the 34^th, because a small part of that day is considered like the whole day.

Despite this, one may sing, play music, and dance on Lag Ba-omer, in honor of the anniversary of R. Shimon bar Yoĥai’s death. However, the other customs of mourning remain binding. Thus, according to this practice, one may not get married or cut one’s hair on Lag Ba-omer, and when the day ends, one may not play music or dance on the night of the 34^th. When the morning of the 34^th comes, however, all practices of mourning cease to apply. (Those who follow Arizal’s customs act stringently and refrain from cutting their hair until Erev Shavu’ot; see Kaf Ha-ĥayim 493:13.)

Some Sephardic communities – like those from Turkey and Egypt – end all customs of mourning on Lag Ba-omer. Even though most Sephardim in Israel today do not follow this practice, if there is a great need to be lenient on Lag Ba-omer or the night of the 34^th, one should consult with a Torah scholar.[3]