When do the mourning customs cease-night or day?[1]

Some Poskim[2] rule that the mourning customs are followed during the night of Lag BaOmer up until after day break. Other Poskim[3], however, rule that the mourning customs cease to be practiced beginning from the night [i.e. Tzeis Hakochavim[4]] of Lag BaOmer. Practically, the main custom follows the latter opinion, and so is the current Chabad custom[5], although some are stringent like the first approach. One may hence get a haircut [unless one follows the Kabalistic custom, as is the Chabad custom] listen to music, get married and recite Shehechiyanu from that time.

[1] See Admur 493:5

[2] 1^st opinion in Admur ibid; Rama 493:2; Kneses Hagedola 493:1; Elya Raba 493:7 [regarding weddings]; Beis David 280; Kitzur SHU”A 120:6; M”B 493:11; Machatzis Hashekel 493:3

Background: The 1^st opinion in Admur ibid states that the mourning customs are followed during the night of Lag BaOmer up until after day break, being that Lag BaOmer is the 33^rd day of mourning, and even on this day there were some students who died [and hence reached the grand total of 24,000 deaths]. The mourning customs end after daybreak of Lag BaOmer, being we always apply the rule of Miktzas Hayom Kikulo to the last day of mourning, as explained in Yoreh Deah 395:1. According to this opinion, from that time and onwards the mourning customs are no longer followed. [Admur ibid; Rama 493:2] So also rules [to cease the customs only after sunrise]: Kneses Hagedola 493:1; Elya Raba 493:7 [regarding weddings]; Beis David 280; Kitzur SHU”A 120:6; M”B 493:11

[3] 2^nd opinion mentioned in Admur 493:5; Peri Chadash 493:2; Mor Uketzial; Machazik Bracha 493:5; Shaarey Teshuvah 493:5; Beir Heiytiv 493:5 in name of Chok Yaakov “Those who do not say Tachanun on Erev Lag BaOmer are likewise to cease the mourning customs by night.”; Lev Chaim 2:97; Mahariy Asaad E.H. 39; Chelkas Yaakov 1:99; Minchas Yitzchak 4:84 based on Chasam Sofer 142 that haircuts and weddings have the same law; Igros Moshe 1:159; Rebbe in Sichas Kodesh 5737 1:703 [printed in Shulchan Menachem 3:34; Shaarey Halacha Uminhag 5:55] based on Siddur Admur that rules like this opinion, that Tachanun is not said on Erev Lag BaOmer.

[4] Nitei Gavriel 48:18

[5] The Rebbe’s opinion: In the early years the Rebbe answered that one should abide by this stringent opinion, to not cease the mourning customs until the day of Lag BaOmer. [Igros Kodesh 8 p. 318; See Otzer Minhagei Chabad p. 284] However in later years the Rebbe finalized, based on Admur in the Siddur, that the mourning customs cease at night and hence weddings may take place then. [Sichas Kodesh 5737 1:703; Shulchan Menachem 3:34] Practically, the Rebbe accepted this as the final ruling and so was the custom in the Rebbe’s neighborhood to wed on the night of Lag BaOmer. [See Hisvadyos 1989 3 p. 178]