Your neighbor is planning on making a wedding on Rosh Chodesh Sivan, while a colleague did so the day after Lag B’Omer (not that he could have done it the day before even if he would have wanted; the halls were all booked on Lag B’Omer itself months in advance). Yet, a friend insists that one must wait until after Shavuos, while another bemoans that he should have made the wedding right after Pesach. Who is correct? Welcome to the annual Sefirah scenario.
The Gemara Yevamos (62b) famously and tragically details the deaths of 24,000 students of Rabbi Akiva during the time period between Pesach and Shavuos, all for not according each other proper honor. Although there are many different rationales given by the commentaries to explain this catastrophe, the Tashbetz (Shu”t vol. 1: 178) elucidates that the reason they were punished so severely for a seemingly minor infraction is that their not treating each other properly ended up engendering a tremendous Chilul Hashem. In fact, according to several authorities, the reason why Lag B’Omer is a day of celebration is that it is the day when Rabbi Akiva started teaching his five new students (including Rabbi Shimon bar Yochai), allowing the Torah’s mesorah to perpetuate; a feat that was previously in jeopardy after the deaths of his talmidim.
This calamity is actually the basis of the annual Sefirah restrictions, which include not getting married or taking a haircut. Yet, that does not properly explain the different and varied minhagim that Klal Yisrael keeps regarding the actual time frames of these restrictions.
And there are different minhagim. In fact, Rav Moshe Feinstein zt”l lists six different customs, and that is not including the Arizal’s minhag. Yet, practically, the Pri Megadim and Mishnah Berurah break it down to three main disparate customs. The others are variations on those main opinions.
Minhag # 1 -Sefardic Sefirah
The Shulchan Aruch writes that one should not get married between Pesach and Shavuos until Lag B’Omer; likewise regarding haircuts, as at that time the Talmidim of Rabbi Akiva stopped dying. Therefore, these restrictions are permitted starting from the next day - Lad B’Omer.
Minhag # 2 - LaG not LaD
However, the Rema argues, stating that the Ashkenazic minhag is to allow these activities from Lag B’Omer itself, and not necessitate waiting until the next day. The reason for the allowance a day earlier than the Shulchan Aruch mandates is either due to the dictum of Miktzas Hayom K’kulo, that part of a day is considered like a full day, or that he held that the Talmidim stopped dying by / on Lag B’Omer and not Lad B’Omer. Additionally, the Rema is following early Ashkenazic authorities such as the Maharil, Mahari Weil, and the Sefer Haminhagim of Rav Yitzchak Isaac Tyrnau (Tirna), all of whom allowed haircuts and celebrations on Lag B’Omer itself. 
Minhag # 3 - Second Sefirah
The Rema then mentions another popular minhag, to only start the Sefirah restrictions from Rosh Chodesh Iyar, and not from right after Pesach. This Sefirah lasts until shortly before Shavuos, excluding Lag B’Omer itself. This has come to be known colloquially as ‘Second Sefirah’.
But why such disparate Sefirahs? If we are all keeping the same prohibitions for the same reason, how can there be so many different minhagim in its practical application?
It turns out that there are two main different rationales expressed by the Rishonim as to when the Sefirah restrictions should actually apply. The first, mentioned as a ‘Midrash’ by R’ Yehoshua ibn Shu’aib and an ‘old Sefardi Sefer’ by the Baal Hamaor and Tashbetz, is that Rabbi Akiva’s Talmidim stopped dying by ‘Parus HaAtzeres’ or the halfway point before Shavuos. Since the Gemara states that we should start to learn the halachos of a Yom Tov 30 days prior to its commencement, which would mean that 15 days before a holiday would be its ‘midpoint’, this would squarely place the ‘Parus’ on Lad B’Omer (49 - 15 = 34). According to this, they stopped dying on Lad B’Omer and therefore all Sefirah restrictions cease on this day as well. As mentioned previously, the Shulchan Aruch states that he follows this opinion, and therefore he rules that from Lad B’Omer, haircuts and weddings are permitted. As mentioned previously, this is the common Sefardi minhag.
However, there is another opinion, attributed to the Baalei Tosafos. They maintain that in actuality the talmidim died throughout the entire time period from Pesach to Shavuos. Yet, they did not die on days when Tachanun was not said, including all days of Pesach, the Shabbosos in between, and Rosh Chodesh. This adds up to 16 days. Meaning, of the entire 49 day period, they died on 33 of those days. Therefore, as a siman to show that they died for 33 of these days (in addition to several other reasons detailed at length in a previous article titled “The ‘Unknown Days’ of the Jewish Calendar”), Lag B’Omer, the 33rd day of the Sefirah, was chosen as a day of easing restrictions.
The question is, which of these minhagim is the Rema following? It is fairly certain that the second Minhag Ashkenaz he delineates, starting from Rosh Chodesh Iyar until shortly before Shavuos (and variations thereof; this will be addressed later on), is following Tosafos’ shitta of 33 days. Since nowadays we don’t say Tachanun the whole month of Nisan, the 33 days start in Iyar and last until the beginning of Sivan. But which opinion is the first custom he cites (from Pesach until Lag B’Omer) following?
The Bach maintains that this minhag as well, follows the shittah of Tosafos. In other words, both minhagim cited by the Rema, ‘First Sefirah’ and ‘Second Sefirah’ are due to keeping 33 days, with the variant minhagim dependant on which 33 days are customarily kept. On the other hand the Vilna Gaon argues that the Rema’s ‘First Sefirah’ minhag is due to following the shittah of the Shulchan Aruch, which is that the Talmidim only died up to Lag B’Omer itself.
However, it is important to note that this discussion of figuring out the Rema’s true intent is not just theoretical. It actually has practical ramifications. And yes, there is a substantial difference between these understandings that just might affect us, and that is the question of the permissibility of switching Sefirahs.
The Chasam Sofer, regarding scheduling weddings during Sefirah, maintained that there is “no contradiction between years” as pertaining to Sefirah observance. This means that even in one town (which needs to follow one minhag), if one year someone got married on Rosh Chodesh Iyar, this does not prevent another from getting married during the Sheloshes Yemei Hagbalah the next year. His psak is widely followed. Additionally, we find that according to many authorities, if there is no set minhag in a certain place (and nowadays, most Jewish communities with no one central authority are considered as such) one may simply choose which minhag to follow. Following this implies that one has the halachic right to choose which Sefirah to keep in any given year, based on whatever specific circumstances affect him that year.
Rav Moshe’s Ruling
However, this is not so clear-cut, nor unanimous. In fact, and although widely and seemingly erroneously quoted as holding that one may indeed switch between ‘First’ and ‘Second Sefirahs’ in different years, Rav Moshe Feinstein zt”l, actually qualified such action. He clarifies that for Ashkenazim to be allowed to do so would depend on the difference of opinions between the Bach and Vilna Gaon as to the interpretation of the Rema’s ‘First Sefirah’. He explains that according to the Bach, that both minhagim are based on keeping 33 days, it technically should not matter which 33 days are kept. Accordingly, one may switch ‘Sefirahs’ in different years.
Yet, according to the Gr”a, the ‘First Sefirah’ is solely due to the Talmidim dying only in the first 33 days of the Omer. If so, questions Rav Moshe, how can one switch ‘Sefirahs’, if each is mutually exclusive, based on different accountings? If one holds that the Talmidim only died up until Lag B’Omer, how can he, in the very next year, follow a different minhag, which is based on a shittah that they did not actually die at that time, or vice versa? Therefore, he maintains that according to the Gr”a one may not switch ‘Sefirahs’ from year to year.
Additionally, Rav Moshe holds that the ‘Second Sefirah’ is the true Ashkenazic minhag and that ‘First Sefirah’ is essentially aSefardic minhag. He therefore concludes that an Ashkenazi may not switch from ‘Second Sefirah’ to the ‘First Sefirah’, as ‘lechatchilla we should not be lenient against the shittah of the Gr”a, except under extremely extenuating circumstances’, but rather only between two different versions of ‘Ashkenazic Sefirah’, in different years, both of which end in different days in Sivan (see Postscript).
However, and although several others contemporary authorities allow only coming for the Chuppah and wishing a brief Mazal Tov, nevertheless, Rav Moshe does fully permit one to attend a wedding of someone who is keeping a different Sefirah, including even staying for the music and dancing. Most poskim, including Rav Yaakov Kamenetsky zt”l, Rav Shlomo Zalman Auerbach zt”l, Rav Yosef Shalom Elyashiv zt”l, Rav Yisrael Yaakov Fischer zt”l, Rav Chaim Kanievsky shlit”a, Rav Moshe Sternbuch shlit”a, and Rav Nissim Karelitz shlit”a, agree with Rav Moshe and allow one who is still keeping his Sefirah to fully participate in a wedding of one who is keeping / kept a different Sefirah.
Although several of these Gedolim write that this applies “if one got married when it was muttar for him to do so”, implying that if one did not keep a proper Sefirah, it may not be permitted for others to stay and rejoice at the chasuna, nevertheless, it is important to note that Rav Moshe Feinstein zt”l (and others who agreed with his reasoning) explicitly permitted attending even in such an occurrence. Rav Moshe explains that the halachah states (Shulchan Aruch, Orach Chaim 493: 1) that if one got married during Sefiras HaOmer (at a time when it was technically forbidden for him to do so) we do not punish him (meaning it is still valid). Rav Moshe writes “that there is no greater punishment for a Chassan and Kallah than having guests refuse to show up and rejoice at their wedding”, and therefore it is still permitted to attend. In a later teshuvah Rav Moshe even allows a guest who would feel uncomfortable attending such a wedding ungroomed, to take a haircut, even though Sefirah restrictions are still personally in affect for him. On the other hand, it is known that his son, Rav Dovid Feinstein shlit”a, generally rules somewhat more stringently nowadays.
In conclusion, now that we have a clearer understanding of the various Sefirah minhagim and their sources, we can appreciate the array of customs followed by our neighbors and friends. And if you do get a wedding invitation inviting you to share in a simchah at some point between Pesach and Shavuos, you will now know how to respond – by asking your local competent halachic authority a proper sheilah.
Postscript: As mentioned previously, there are many variations as to the exact starting and ending dates for the Sefirah, and especially ‘Second Sefirah’. For example, there is the Rema’s basic ‘Second Sefirah’, which starts after Rosh Chodesh Iyar, breaks for Lag B’Omer, and continues until Erev Shavuos, as well as its alternative, the Magen Avraham, Chayei Adam, Aruch Hashulchan, and Mishnah Berurah’s minhag, which starts from and includes Rosh Chodesh Iyar until the Sheloshes Yemei Hagbalah, with a break on Lag B’Omer. Another common minhag is the Derech Hachaim’s minhag which starts from Isru Chag Pesach, skips Rosh Chodesh Iyar and Lag B’Omer, and ends by Rosh Chodesh Sivan. Another interesting custom is the Elyah Rabbah’s minhag, keeping the entire Sefirah excluding Lag B’Omer, and concluding on Erev Shavuos. Another variation is the Taz’s custom, to keep the ‘First Sefirah’ for haircuts, but to continue with the prohibition on weddings after Lag B’Omer until shortly before Shavuos; due to the horrific tragedies perpetuated by the Crusaders to many Ashkenazic communities during the second half of Sefirah (Gezeiras Tatn”u). And of course, there is the well-known minhag of the Arizal, which is to keep the entire Sefirah for haircuts, including Lag B’Omer, until Erev Shavuos. One should check with his knowledgeable Rabbinic authority as to which exact minhag he should personally follow.
The author wishes to thank Rabbi Naftali Zvi Frankel for providing several important sources and for being the impetus for this author’s interest and research on this topic.
This article was written l’iluy nishmas Asher Zelig ben Zev a”h, Mr. Arthur Graff, my wife’s grandfather, who was niftar in the past few weeks, and l’Zechus for Shira Yaffa bas Rochel Miriam v’chol yotzei chalatzeha for a yeshua sheleimah teikif u’miyad!
Rabbi Yehuda Spitz, author of M’Shulchan Yehuda, serves as the Sho’el U'Meishiv and Rosh Chabura of the Ohr Lagolah Halacha Kollel at Yeshivas Ohr Somayach in Yerushalayim.
For any questions, comments or for the full Mareh Mekomos / sources, please email the author: firstname.lastname@example.org.
 See Pri Chodosh (Orach Chaim 493) and Chida (Tuv Ayin 17: 493 and Shiyurei Bracha, Orach Chaim 493: 1). However, the Yalkut Me’am Loez (Parshas Emor) and Sdei Chemed (Ma'areches Eretz Yisrael, 6) maintain that Rabbi Akiva actually bestowed Semichah on his five new talmidim on this day.
 There are also other reasons cited for these prohibitions. See Chok Yaakov (Orach Chaim 493; 3; citing the Shibolei Leket) that according to Rav Yochanon ben Nuri (Ediyos Ch. 2: Mishnah 9) Reshaim are judged in Gehinnom between Pesach and Shavuos. Additionally, he writes that these days are ‘Yemei Din’ on grain, which is why the Korban Omer comes from barley. The Arizal (Shaar HaKavanos, Inyan Sefiras HaOmer, Drush 12; cited by the Shaarei Teshuvah, Orach Chaim 493: 8), who mandates keeping the entire Sefirah up until Erev Shavuos (including Lag B’Omer) is quoted as holding so for a different reason, a Kabbalistic prohibition, exclusive only to hair and not necessarily related to aveilus associated with Sefiras HaOmer. See Shu”t Minchas Elazar (vol. 4: 44) at length about this, as well as Shu”t Divrei Yoel (vol. 1, Orach Chaim 26: 1).
 Shu”t Igros Moshe (Orach Chaim vol. 1: 159). See also sefer Bein Pesach L’Shavuos (ppg. 223 – 240) who details 10 different minhagim of Sefirah (!).
 Pri Megadim (Orach Chaim 493, Mishbetzos Zahav 1), and Mishnah Berurah (Biur Halacha (493: 3 s.v. yesh). However, they do not actually agree as to the reasons behind one of the three minhagim, the Rema’s ‘First Sefirah’. See footnote 13. However, the Aruch Hashulchan (ad loc. 7) holds that there are really only two main minhagim. See footnote 6.
 Shulchan Aruch (Orach Chaim 493: 1 and 2). Although the K af Hachaim (ad loc. 11) opines that there truly is no machlokes between the Shulchan Aruch and Rema, and both truly mean that weddings are permitted from Lag B’Omer on and not Lad B’Omer, it must be noted that this understanding is categorically rejected across the board, as in his Beis Yosef commentary, the Shulchan Aruch wrote that the Talmidim died a full 33 days and the restricted activities are only permitted from the following day. This is the understanding of virtually every later authority, whereby the Shulchan Aruch and Rema are arguing about the permissibility to wed on Lag B’Omer itself. See Pri Megadim (ibid.), Biur Halacha (ibid.), Shu”t Yabea Omer (vol. 3, Orach Chaim 26; at length), Shu”t Minchas Yitzchak (vol. 4: 84, 12), Shu”t Yechaveh Daas (vol. 3: 31), Chazon Ovadiah (Yom Tov, pg. 255), Rav Mordechai Eliyahu’s Darchei Halacha glosses to the Kitzur Shulchan Aruch (120: 8) and Yalkut Yosef (Kitzur Shulchan Aruch, Orach Chaim 493: 1). The Minchas Yitzchak and Rav Ovadiah Yosef both maintain that only in extenuating circumstances may a Sefardi be permitted to get married on Lag B’Omer itself.
 Rema (ad loc.). However, there is some debate among later authorities as to his intent, whether he is actually agreeing to the Shulchan Aruch’s reasoning and just arguing about which day the Talmidim stopped dying or whether he is subscribing to a completely different rationale. This will be explained further in the article. See footnote 15. However, it must be noted that the Aruch Hashulchan (ad loc. 7) understands that there are only two main shittos, and that the Rema only holds of ‘Second Sefirah’. Accordingly, what the Rema is disagreeing with the Shulchan Aruch about Lag B’Omer is that he is saying that even the Shulchan Aruch would agree, due to other reasons, that on Lag B’Omer weddings and haircuts should nonetheless be permitted.
 Maharil (Dinei Hayamim Shebein Pesach L’Atzeres ppg. 156 - 157; 7 - 8), Mahari Weil (Dinim U’Minhagim 51), and Sefer Haminhagim (Hilchos Chodesh Iyar pg. 66). See Darchei Moshe (Orach Chaim 493: 1).
 Although the Rema (and most other authorities - see Mishnah Berurah ad loc. 11 and Shaar Hatziyun 12) explicitly only allows weddings and haircuts etc. on the day of Lag B’Omer due to the Talmudic dictum of ‘Miktzas Hayom K’kulo’ and is therefore only permitted from after Haneitz Hachamah, nevertheless, there are several authorities who are lenient in permitting haircuts even from the preceding evening, at the start of Lag B’Omer, including the Tosafos Yom Tov (Malbushei Yom Tov ad loc. 2), the Elyah Rabbah (ad loc. 7 and Elyah Zuta 6; however he holds that this only applies to haircuts and not weddings), Rav Yaakov Emden (Mor U’Ketziah ad loc. s.v. b’hagahas), and Shaarei Teshuvah (ad loc. 5), and is cited as a ‘yesh omrim’ by the Chok Yaakov (ad loc. 6) and Shulchan Aruch HaRav (ad loc. 6).
 There are many variations of this opinion, when this period actually starts and ends. These will be explained further on.
 Drashos R”I Ibn Shu’aib (Yom Rishon Shel Pesach pg. 41b, 2nd column), Shu”t Tashbetz (vol. 1, 178; citing the Baal HaMaor). Also cited by the Abudraham (pg. 245) quoting Even Hayarchi (Hamanhig, Hilchos Erusin end 106), and Rabbeinu Yerucham (Sefer HaAdam, Nesiv 5, vol. 4, pg. 44b, 2nd column, in a later Hosafa to the sefer). According to all of these Rishonim only on Lad B’Omer would haircuts and weddings be permitted.
 ‘Parus HaAtzeres’ is cited in Gemara (Yerushalmi) Shekalim 2a; see Korban HaEidah (ad loc. s.v. b’parus). See also Gemara Bechoros 58a.
 See Shulchan Aruch (Orach Chaim 493: 1 and 2), Pri Megadim (ad loc. Mishbetzos Zahav 1), Biur Halacha (ad loc. s.v. yesh), Kaf Hachaim (ad loc. 11), Shu”t Yabea Omer (vol. 3, Orach Chaim 26), Shu”t Minchas Yitzchak (vol. 4: 84, 12), Shu”t Yechaveh Daas (vol. 3: 31), Chazon Ovadiah (Yom Tov, pg. 255), Rav Mordechai Eliyahu’s Darchei Halacha glosses to the Kitzur Shulchan Aruch (120: 8), and Yalkut Yosef (Kitzur Shulchan Aruch, Orach Chaim 493: 1).
 These reasons include being the day when the Mann (manna) started to fall, feeding Bnei Yisrael in the Midbar; the day when Rabbi Shimon bar Yochai and his son, Rabbi Elazar came out of the cave they hid in for 13 years; it possibly is Rabbi Shimon bar Yochai’s Yahrtzeit (however, it is important to note that this understanding might actually be based on a simple printing mistake, and many authorities including the Chida and Ben Ish Chai, maintain that Lag B’Omer is not truly his Yahrtzeit); the day when Rabi Akiva gave Semichah to his five new students (including Rabbi Shimon bar Yochai) after the 24,000 died, allowing the Torah’s mesorah to perpetuate; and the day when Rabi Shimon bar Yochai’s hidden Torah, the Zohar, became revealed to the world.
 This shittah, credited to Tosafos, is also first mentioned in the Drashos R”I Ibn Shu’aib, and cited by many later authorities. See Beis Yosef (Orach Chaim 493: 1). An additional reason, posited by the Levush (Orach Chaim 493: 3), is that the Talmidim did not actually die on Lag B’Omer itself, but did prior to and immediately following until Shavuos.
 Bach (Orach Chaim 493 s.v. u’mah) and Vilna Gaon (Biur HaGr”a ad loc. 8). Interestingly, the Pri Megadim (ad loc. Mishbetzos Zahav 1) and Aruch Hashulchan (ad loc. 7; cited in footnote 6) imply that they understood the machlokes between the Shulchan Aruch and Rema akin to the Bach, yet, the Shulchan Aruch Harav (ad loc. 5), Mishnah Berurah (Biur Halacha 493: 3 s.v. yesh; at length), and Kaf Hachaim (ad loc. 11) seem to understand the machlokes as the Gr”a did.
 Shu”t Chasam Sofer (Orach Chaim 142; also cited briefly in his glosses on Shulchan Aruch Orach Chaim 493). He also maintains that there is no tarti desasri between haircuts and weddings. Meaning, one may keep one Sefirah regarding haircuts and another regarding weddings.
 See, for example, Shu”t Maharitz (Dushinsky) (vol. 1: 45) at length.
 As detailed in Shu”t Igros Moshe (Orach Chaim vol. 1: 159).
 Including the Chok Yaakov (Orach Chaim 493: 2), Shulchan Aruch Harav (ad loc. 7), Mishnah Berurah (ad loc. 17), and Kaf Hachaim (ad loc. 51).
 See, for example, Rabbi Shimon Eider’s SeferHilchosPesach(vol. 2, Ch. 19, pg. 332, 4)and the Dirshu edition of the MishnahBerurah(493: Biurum V’Hosafos 33) who quote Rav Moshe as allowing switching between ‘First’ and ‘Second’ Sefirahs, and not how Rav Moshe himself actually concludes in his teshuvos. Interestingly, Rabbi Eider quotes Rav Aharon Kotler zt”l as holding that one may not switch ‘Sefirahs’ unless in case of necessity and with Hataras Nedarim, which actually turns out quite similar to Rav Moshe’s actual psak.
 See Shu”t Igros Moshe (Orach Chaim vol. 1: 159) at length. This can also be seen from a later teshuvah (Shu”t Igros Moshe, Orach Chaim vol. 2: 95, s.v. hinei) where he explains that an Ashkenazi may only lechatchilla switch ‘Sefirahs’ from one Ashkenazic minhag to another and he gives examples of keeping from Isru Chag Pesach to Rosh Chodesh Sivan (minus both days of Rosh Chodesh and Lag B’Omer), or from Rosh Chodesh Iyar to the Sheloshes Yemei Hagbalah, with no mention of keeping ‘First Sefirah’ as a viable option.
 Bach (Orach Chaim 493 s.v. u’mah) and Vilna Gaon (Biur HaGr”a ad loc. 8). Interestingly, the Pri Megadim (ad loc. Mishbetzos Zahav 1) and Aruch Hashulchan (ad loc. 7) imply that they understood the machlokes between the Shulchan Aruch and Rema akin to the Bach, yet, the Shulchan Aruch HaRav (ad loc. 5), Mishnah Berurah (Biur Halacha 493: 3 s.v. yesh; at length), and Kaf Hachaim (ad loc. 11) seem to understand the machlokes as the Gr”a did. For more on Rav Moshe’s understanding of possible distinctions between the shittos of the Bach and Gr”a, see the recent Shu”t V’Debarta Bam (vol. 2: 201).
 Which he implies at the end of his teshuva and is attested to by both Talmidim and family. See Rabbi Avrohom Blumenkrantz zt”l’s annual Kovetz Hilchos Pesach (in his Chapter on Sefiras HaOmer, ex. 5766 / 2006, pg. 257), Kovetz L’Torah V’Hora’ah (Sefer Zikaron for Rav Moshe 5749, pg. 211; article by Rav Elimelech Bluth), Shu”t V’Debarta Bam (vol. 1: 141 s.v. v’shamati; quoting Rav Dovid Feinstein shlit”a), and Mesores Moshe (vol. 1, pg. 153: 319). Although the Rema (Orach Chaim 493: 2 & 3; in fact in his Darchei Moshe ad loc. 3) he writes that ‘v’nirah she’ein shume echad min haminhagim who ta’us, rak shelo yinhagu heter b’shneihem’, Bach (ibid.), Taz (ad loc. 2; he does however, add that it is proper to keep the whole Sefirah regarding the wedding prohibition due to the horrific tragedies perpetuated by the Crusaders during the second half of Sefirah), Chasam Sofer (ibid.; ‘lo pashat eleh ad Lag, u’minhag Ashkenazim m’Lag v’eilech aineni minhag kavua kol kach’), and Rav Chaim Kanievsky shlit”a (Shoneh Halachos vol. 3: 493, 1), seem to hold that ‘First Sefirah’ is an authentic Ashkenazic one as well, the idea that the proper Ashkenazic minhag is indeed the second one is cited by many authorities including the Chayei Adam (vol. 2; 131, 11; who only cites ‘Second Sefirah’), the Butchatcher Gaon (Eishel Avraham, Tinyana, Orach Chaim beg 493; ‘b’medinos eilu shenohagim lehachmir m’Lag B’Omer ad Rosh Chodesh Sivan’), the Aruch Hashulchan (ad loc., 6; ‘v’chein hu minhag shelanu’), the Divrei Malkiel (Shu”t vol. 3: 23), the Melamed L’Hoyeel (vol. 1: 113, 22), the Mishnah Berurah (493: 5 and 15; ‘l’didan’), the Minchas Yitzchak (Shu”t vol. 4: 84, 4), the Maharitz Dushinsky (Shu”t ibid.), Rav Yosef Eliyahu Henkin zt”l (in his annual Luach Ezras Torah and in his posthumously published Shu”t Gevuros Eliyahu,vol. 1 - Orach Chaim 150: 2 and footnote 1013), and Rav Shlomo Zalman Auerbach zt”l (Halichos Shlomo, Moadim vol. 2: Ch. 11, Dvar Halacha 28 and footnote 69).
 According to his son, Rav Dovid Feinstein shlit”a, as quoted in Shu”t V’Debarta Bam (vol. 1: 141 s.v. v’shamati), Rav Moshe’s intent with his allowance ‘b’shaas had’chak gadol’ here, refers to a scenario that is ‘ee efshar b’inyan acher’, such as chassan who was drafted to the army before Shavuos, that he can rely on ‘First Sefirah’ and get married after Lag B’Omer.
 See Kovetz M’Bais Levi (vol. 3: pg. 38, 1), and Shu”t Shraga HaMeir (vol. 6: 92, 3). The Minchas Yitzchak (Shu”t vol. 4: 84, 11 s.v. v’haseder) implies this way as well.
 Shu”t Igros Moshe (Orach Chaim vol. 1: 159 and vol. 2: 95).
 See Emes L’Yaakov on Tur and Shulchan Aruch (Orach Chaim 493: footnote 465), Halichos Shlomo (Moadim vol. 2: Ch. 11, 19), Ashrei HaIsh (Orach Chaim vol. 3: Ch. 65, 30; and especially those following ‘Minhag Eretz Yisrael’ - see footnote 31), Halichos Even Yisrael (vol. 1, pg. 217: 22), Doleh U’Mashkeh (pg. 193: footnote 517), Teshuvos HaGra”ch (vol. 2: pg. 744), Moadei HaGra”ch (vol. 1, 175: pg. 82), Shu”t Teshuvos V’Hanhagos (vol. 4: 128; however he does add that if there are many people dancing and if one abstains from dancing it will not be noticed, it would be preferable for him not to dance as it is still ‘his Sefirah’), Chut Shani (Shabbos vol. 4: Kovetz Inyanim pg. 380), and Netei Gavriel (Pesach vol. 3: Ch. 48, 13).
 Shu”t Igros Moshe (Orach Chaim vol. 1: 159 s.v. v’hinei Chasam Sofer and Orach Chaim vol. 2: 95 s.v. u’lchein).
 It is known (see Rabbi Yitzchak Dovid Frankel’s Kuntress Yad Dodi, Hilchos Sefirah, Questions 1 - 7) that his son, Rav Dovid Feinstein shlit”a rules more stringently nowadays. He maintains that these days when it is widely known that Sefardim mainly keep the ‘First Sefirah’, if an Ashkenazi does so and makes a wedding during ‘Second Sefirah’, it is considered ‘Poretz Geder’ and rules that generally it is preferable not to attend an Ashkenazic wedding during ‘Second Sefirah’, except to say Mazal Tov. According to Rav Dovid’s talmid muvhak, Rav Baruch Moskowitz, author of Shu”t V’Debarta Bam, this is indeed Rav Dovid’s general rule. Yet, there are certain instances when Rav Dovid would indeed allow one to attend, i.e. familial obligations etc. One must always make sure to ask a proper sheilah from his Rav if such a situation arises.
 This was discussed at length in the article, and cited as proper by the Bach (Orach Chaim 493 ibid.), and considered the Rema’s basic minhag by the Pri Megadim (ad loc. Mishbetzos Zahav end 1) and Mishnah Berurah (ad loc. 14). Both this and the next alternative (Sheloshes Yemei Hagbalah), are considered proper and viable options by many Ashkenazic authorities, including the Shulchan Aruch HaRav (ad loc. 5), Kitzur Shulchan Aruch (120: 7), and Rav Moshe Feinstein zt”l (Shu”t Igros Moshe, Orach Chaim vol. 2: beg. 95). For more on the various ‘Sefirahs’, see sefer Bein Pesach L’Shavuos (pg. 223 – 240) at length.
 Magen Avrohom (Orach Chaim 493: 4), Chayei Adam (vol. 2: 131, 11), Aruch Hashulchan (Orach Chaim 493: 6), and Mishnah Berurah (ad loc. 5 and 15). This is also the proper minhag cited by Rav Yosef Eliyahu Henkin zt”l (in his annual Luach Ezras Torah and in his posthumously published Shu”t Gevuros Eliyahu, Orach Chaim 150: 2; although he adds ‘v’hamedrin machmirin gam b’Rosh Chodesh Iyar’).
 Derech Hachaim (Dinim HaNohagim Bein Pesach L’Atzeres, 1 and 4; cited by the Mishnah Berurah (493: end 15). Although the Mishnah Berurah (Shaar Hatziyun ad loc. 13) questions this minhag, several other authorities endorse it, including the Melamed L’Hoyeel (Shu”t vol. 1: 113, 22; although this is not exact, it does involve actively skipping and ending by Rosh Chodesh Sivan), the Divrei Malkiel (Shu”t vol. 3: 23; at length), and Rav Moshe Feinstein zt”l (Shu”t Igros Moshe, Orach Chaim vol. 1: 159, end s.v. v’hinei matzinu). The Pri Megadim (Orach Chaim 493, Eshel Avraham end 5) implies that this was his minhag as well. In fact, a similar minhag (including Rosh Chodesh Iyar but skipping Lag B’Omer and concluding by Rosh Chodesh Sivan), is considered ‘Minhag Eretz Yisrael’ by Rav Yechiel Michel Tukachinsky’s Luach Eretz Yisrael (end Chodesh Nisan s.v. isru chag and beg. Chodesh Sivan), and denoted the proper one by Rav Yosef Shalom Elyashiv zt”l (as cited in Ashrei HaIsh, Orach Chaim vol. 3, Ch. 65: 29 - 30, pg. 434 - 435) and Rav Yisrael Yaakov Fischer zt”l (Halichos Even Yisrael ibid.). Additionally, I have heard from my esteemed father-in-law, Rabbi Yaacov Tzvi Lieberman, b’sheim Rav Moshe Bick zt”l, that the Derech Hachaim’s shittah is the true ‘Minhag America’. The reason for this minhag is that it incorporates 33 days of Aveilus over the Sefirah period – as it essentially accounts for the whole Sefirah, but subtracts the days when we are not noheg Aveilus, including the rest of Pesach, all the Shabbosos, Rosh Chodesh Iyar, and Lag B’Omer.
 See Elyah Zuta (Orach Chaim 493: 5), who maintains that this is the proper minhag, as aside for his grandfather, the Mahara”sh, being noheg this way, this is also the mashmaos of the Maharil (Dinei Hayamim Shebein Pesach L’Atzeres pg. 157: 8) and Levush (Orach Chaim 493: 2) as the correct minhag. This is also the minhag of the Matteh Moshe (688).
 Taz (Orach Chaim 493: 2).
 The Arizal (Shaar HaKavanos, Inyan Sefiras HaOmer, Drush 12; cited by the Shaarei Teshuva, Orach Chaim 493: 8) mandates keeping the entire Sefirah for haircuts up until Erev Shavuos, and including Lag B’Omer. Yet there is some debate whether he would have allowed weddings on Lag B’Omer. The Minchas Elazar (Shu”t vol. 4: 60) asserts that the Arizal would have permitted weddings on Lag B’Omer, as his reasoning for the prohibition mainly concerns haircuts and not weddings, adding that the renowned Divrei Chaim of Sanz married off a child on Lag B’Omer. Yet, the Satmar Rebbe, Rav Yoel Teitelbaum zt”l (Shu”t Divrei Yoel vol. 1, Orach Chaim 26: 1) maintains that those who follow the Arizal may not get married during Sefirah at all, and instead must wait until after Shavuos.
Disclaimer: This is not a comprehensive guide, rather a brief summary to raise awareness of the issues. In any real case one should ask a competent Halachic authority.
L'iluy Nishmas the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga, Rav Yaakov Yeshaya ben R' Boruch Yehuda.