Ethics

Bar Mitzvah-ed Before His Time?

by Rabbi Yehuda Spitz
The Color of HeavenArtscroll

Mein Alte Shachein”, the esteemed Bobover Rebbe, Rav Shlomo Halberstam zt”l, was known to have remarked[1] that he personally started laying Tefillin as a Bar Mitzvah Bochur one day prior to his Bar Mitzvah. His intent was not that the Bobov minhag was to prepare for a Bar Mitzvah by laying Tefillin only one day before the actual Bar Mitzvah, but rather that he himself was full-fledge “Bar Mitzvah-ed” (in the vernacular) before the date of his Bar Mitzvah! The reason why is quite interesting, due to a cosmic “quirk” in our calendar; one that actually comes up again this year.

30 Days Has November…

As is well known from Chazal, and actually millennia later approbated by NASA[2], the Lunar Month is 29 days, 12 hours and 793 chalakim (or 44 minutes and one cheilek). In the times of Chazal, based on eyewitness accounts of the New Moon, any month could have had 30 days (called a chodesh malei or full month) or 29 days (referred to as a chosesh chaseir). In our 19-year cycle Jewish calendar, established by Hillel II (HaZakein), every other month alternates between 29 and 30 days. Whereas the Gregorian calendar maxim might be “Thirty Days has September, April, June, and November”, in the Jewish calendar the colloquialism would probably be “Thirty Days has Tishrei, Shevat, Nissan, Sivan, and Av. Teves, Adar[3], Iyar, Tamuz, and Elul only have 29 days[4]”.

An easy way to tell if the month you are in has 29 or 30 days is by seeing how many days of Rosh Chodesh the following month has. If it has two-days of Rosh Chodesh, that means the first day of Rosh Chodesh is actually the 30th day of the preceding month. For example, the first day of Rosh Chodesh Elul is actually Lamed Av. Even so, since it is connected to the month of Elul, there are halachos how the date is supposed to be written in official documents. Take our date of Lamed Av. Halachically it is to be written as “Rosh Chodesh Elul, Shehu Yom Shloshim L’Chodesh (which is the thirtieth of the month of) Av”[5]. On the other hand, if it is a one-day Rosh Chodesh, it is simply the 1st of that month.

Wild Cards?

As you probably realized, there were two months missing from the “adage of the months”. Cheshvan and Kislev were not mentioned. The reason is that there is no hard and fast rule regarding them. They are the only months that can either have 29 or 30 days depending on the year. Some years both are chaseirim; other years both are malei’im, and others one is chaseir and the other malei. The reasons and rules governing the whys and whens are too complicated for this discussion; suffice to say that when the Mishna Berura discusses this issue he simply writes “ain kanmakom l’ha’arich”, that this is not the place to expound in detail[6]. What is a given is that this is one of the changing variables in our set calendar. In fact, it is this variable that allows a Bar Mitzvah to occur before the actual Bar Mitzvah date.

Will the Real Adar Please Stand Up?

But this is not the only time that a calendar quirk changes a Bar Mitzvah. It is widely known that adding a leap year into the mix always has interesting Bar Mitzvah ramifications. The majority consensus is that if a boy was born in a non-leap year, one in which there was only one Adar, and on the year of his Bar Mitzvah there are two Adars, his Bar Mitzvah will occur in the second Adar, since it is considered the true one[7]. The same holds true if he was actually born in Adar Sheini. In fact the only way one would celebrate a Bar Mitzvah in the first Adar is if he was actually born in an Adar Rishon.

This makes for a remarkable dichotomy. If one boy is born on the 21st of Adar Rishon, and his buddy a week and a half later on the 2nd of Adar Sheini, then in any standard year that follows, the second one would be celebrating his birthday almost 3 weeks before his “older” friend. Since there is only one Adar, the second born’s birthday would be the 2nd of Adar while his “older” friend’s would be on the 21st. In fact, only in a leap year would the older one truly be considered older. This would also affect their Bar Mitzvahs. If their Bar Mitzvah is in a standard year, the younger lad would become a man several weeks before his older compadre[8].

One Day

In a similar vein, we find that if a boy was born on the 30th of Cheshvan (obviously in a year that Cheshvan was malei), which would also be the first day of Rosh Chodesh Kislev, and in his Bar Mitzvah year Cheshvan is a chaseir, meaning there is no 30th, our little lad does not become a man until the 1st of Kislev[9]. The reason is that halachically one cannot truly become a Bar Mitzva until he completes 13 entire years[10]. Since there is no 30th of Cheshvan in his Bar Mitzvah year, he does not actually reach that milestone until the next day, which is Rosh Chodesh Kislev.

Yet it is when the flip side of that equation occurs that it gets really interesting. The Elyah Rabba, based on a ruling of the Bach[11], maintains that if a boy is born on the 1st of Kislev in a year when Cheshvan had only 29 days, and in his Bar Mitzvah year Cheshvan has 30 days, then the boy becomes Bar Mitzvah on the first day of Rosh Chodesh Kislev, which is actually the 30th of Cheshvan! Since he completes 13 full years on that day (as there now is an extra day added to that year), he is obligated in Mitzvos on the day prior to his birthday! His birthday might be Alef Kislev, but his Bar Mitzvah is Lamed Cheshvan[12]!

Although the Birur Halacha opines that it might still be preferable not to count this boy for a minyan until his actual birthday[13], and the rule would not apply for yahrtzeits[14], nevertheless, this obscure ruling of becoming a Bar Mitzvah before the birthday is actually cited as halacha by the consensus of many great Acharonim, including the Shaarei Teshuva, Chavas Daas, Rav Akiva Eiger, Pri Megadim, Machatzis HaShekel, Levushei Srad, Mishna Berura and Kaf Hachaim[15].

BaYamim HaHeim BaZman HaZeh

This is why the great Bobover Rebbe zt”l claimed he became Bar Mitzvah one day before his Bar Mitzvah date. He was born on Alef Kislev in a year when Cheshvan was chaseir (5668), and in his Bar Mitzvah year (5681) Cheshvan was malei.

This fascinating, albeit relatively unknown, psak would apply to this upcoming Rosh Chodesh Kislev as well. For, 13 years ago (5761), Cheshvan had only 29 days and this year (5774) it has the full 30 days. Therefore, a young lad who was born on the 1st of Kislev almost 13 years ago, and who is now on the cusp of manhood, would actually become Bar Mitzvah on the first day of Rosh Chodesh Kislev, which is actually the 30th of Cheshvan 5774, and not on his actual birthday, the second day of Rosh Chodesh Kislev, which is the 1st of Kislev.

The Gemara in Shabbos (75a) stresses the importance of knowing the calculations of our calendar, with many Rishonim understanding that there is a specific mitzvah to do so. The Chazon Ish[16] explicitly mentions the calculations of the Lunar Month as a prime example of this. Now, at least we can say we are one step closer.

The author wishes to thank R’ Shloime Lerner for raising awareness of this unique issue, and whose Mareh Mekomos served as the impetus for this author’s interest and research in this topic. We would like to wish him a hearty Mazal Tov on his grandson’s becoming Bar Mitzvah this Sunday, Rosh Chodesh Kislev, one day prior to his actual birthday.



[1]See Gilyon Shoneh Halachos, Chodesh Nissan 5771, pg. 11, ina letter from Rav Yehoshua Shalom Nosson Rubin. Thanks are due to R’ Shloime Lerner for sending me this source.

[2]Rabban Gamliel’s statement (mekublani m’bais avi abba) in Gemara Rosh Hashana 25a. See Rambam (Hilchos Kiddush HaChodesh Ch. 6, 2 & 3), Tur’s Seder HaKvius, Mishna Berura’s Seder La’asos Luach B’Ketzara (end O.C. 428), and Chazon Ish (O.C. 138, 4). This comes out to 29.53059 days. According to “Discovery” by Rabbi Shraga Simmons (pg. 31), “After years of research based on calculations using satellites, hairline telescopes, laser beams, and super computers, scientists at NASA have determined that the length of the ‘synodic month’, the time between one new moon and the next, is 29.530588 days”!

[3]This is in a regular year; in a leap year Adar Rishon would have 30 Days and Adar Sheini would have 29.

[4]See Biur Halacha (428, 1, end s.v. eilu hayamim).

[5]This wording follows the Shulchan Aruch’s opinion (O.C. 427, 1). However, the Bach (ad loc. s.v. v’kosvin) and Pri Megadim (ad loc. M.Z. 1) maintain that the order should be reversed and written as “Yom Shloshim L’Chodesh Av, Shehu Yom Rosh Chodesh Elul’. See Mishna Berura (ad loc. 1).

[6]Biur Halacha (428, 1, end s.v. eilu hayamim).

[7]Rema (O.C. 55, 10; based on Shu”t Mahar”i Mintz 15), Levush (O.C. 685, 1), Magen Avraham (O.C. 55, 10), Pri Chadash (ad loc. 10), Pri Megadim (ad loc. E.A. 10), Levushei Srad (ad loc. s.v. eino), Korban Ha’Eida (Megillah Ch. 1, Shiyarei HaKorban s.v. hada), Shaarei Teshuva (O.C. 55, 11), Kitzur Shulchan Aruch (15, 2), Aruch Hashulchan (O.C. 55, 14), Mishna Berura (ad loc. 45), and Kaf Hachaim (ad loc. 59); not like the Mahara”Sh HaLevi (Shu”t O.C. 16). However, this might not hold true for observing yahrtzeits, as that is a machlokes between the Shulchan Aruch and Rema (O.C. 568,7), as explained by the Mishna Berura (ad loc. 41) as to which Adar is ikar for that. See also Shu”t Igros Moshe (Y”D vol. 3, 160) who concludes that even for yahrtzeits the essential Adar is Adar Sheini.

[8]Although the Magen Avraham (ibid., based on his understanding of the Mahar”i Mintz’s position) maintains that even a boy born in an Adar Rishon’s Bar Mitzva gets deferred to Adar Sheini, and the Olas HaTamid agrees with him, nevertheless, the consensus of poskim is that one who is born in an Adar Rishon’s Bar Mitzvah is observed in Adar Rishon as well; if he was born in a standard Adar or Adar Sheini his Bar Mitzvah would be observed in Adar Sheini. These poskim include the Shulchan Aruch (ibid.), Levush (O.C. 685, 1), Pri Chadash (ad loc. 10), Shvus Yaakov (Shu”t vol. 1, 9; who writes that the Magen Avraham misunderstood the Mahar”i Mintz), Elya Rabba (O.C. 55, 9 & Elya Zuta 5), Rav Dovid Oppenheim (cited in the Ba’er Heitiv ad loc. 11), Me’il Tzadaka (Shu”t 21), Shaarei Teshuva (O.C. 55, 11), Ma’amar Mordechai (ad loc. 13), Pri Megadim (ad loc. E.A. 10), Ikrei HaDat (3, 7), Maharsham (Daas Torah ad loc. s.v. u’shnas), Kitzur Shulchan Aruch (15, 2), Aruch Hashulchan (O.C. 55, 14), Mishna Berura (ad loc. 43), and Kaf Hachaim (ad loc. 59). The Ba’er Heitiv (ibid.) concludes that “v’chein haminhag pashut eitzel kol ba’alei hahora’ah”! On an anecdotal level, this halacha affected me growing up as my birthday was Rosh Chodesh Adar and my Bar Mitzvah occurred on a leap year. I am certain it will affect my son who was born on my birthday as well.

[9]Magen Avraham (O.C. 55, end 10 s.v. u’mi), Elya Rabba (ad loc. 9), Levushei Srad (ad loc. s.v. d’naaseh), Derech Hachaim (Dinei Kaddish B’Asarah 4), Shulchan Aruch HaRav (O.C. 55,13 ), Mishna Berura (ad loc. 45), Kaf Hachaim (ad loc. 60).

[10]See Shu”t HaBach (HaYeshanos 145), Sm”a (E.H. 35, 2), Elya Zuta (O.C. 55, 4), Magen Avraham (ad loc. 10), Ba’er Heitiv (ad loc. 11), and Mishna Berura (ad loc. 45).

[11]Elya Rabba (O.C. 55, end 9) based on the Bach (Shu”t HaBach HaYeshanos 145).

[12]A potential additional reason for this ruling is that the Aruch LaNer (Shu”t Binyan Tzion 151) maintains that both days of Rosh Chodesh have a status of one day (meaning they are considered somewhat connected). Therefore, once our growing lad’s 13 years are complete and it is already Rosh Chodesh (as he was born on Rosh Chodesh) he would already be considered a Bar Mitzvah, even though his true birthday is the following day (of Rosh Chodesh). The Aruch Hashulchan (O.C. 55, end 15) implies this way as well, and this logic is also mentioned in Ishei Yisrael (pg. 135, Ch. 15, footnote 26, inthe parenthesis).

[13]Birur Halacha (Rav Yitzchak Isaac Zilber, in his comments on the Mishna Berura ibid., pg. 133). He opines that although our protagonist may take on the Mitzvos of a Bar Mitzva Bochur, it is nonetheless preferable to wait until his actual birthday to count him for a minyan or zimun, unless it is shaas hadchak. As mentioned this is not the normative halacha.

[14]An interesting side point is that this ruling would not apply to yahrtzeits (see Yoreh Deah 402, 1; Magen Avraham O.C. 568, 20; Taz Y”D 65, 8; and Aruch Hashulchan O.C. 568, 15). The reason is that a yahrzeit is observed on the date when someone is niftar; therefore it has to be on the date. Whereas a child becomes Bar Mitzvah on the day he completes 13 full years.

[15]Shaarei Teshuva (O.C. 55, 11), Chavas Daas (Derech Hachaim, Dinei Kaddish B’Asarah, end 4), Rav Akiva Eiger (O.C. 55, 10 s.v. v’am”sh), Pri Megadim (ad loc. E.A. 10), Machatzis HaShekel (ad loc. s.v. ad sheyavru), Levushei Srad (ad loc. s.v. ad sheyavru), Mishna Berura (ad loc. end 45), Kaf Hachaim (Falaji 13, 2 and Sofer O.C. 55, 60), Amudei Hashulchan (on Kitzur Shulchan Aruch 15, 1), Ishei Yisrael (pg. 135, Ch. 15, footnote 26, inthe parenthesis). The Elya Rabba adds that the Magen Avraham would even be maskim to this! The Aruch Hashulchan (ad loc. end 15 implies) this way as well.

[16]They are divided though, whether it is a Mitzva D’Oraysa or DeRabbanan. See Rabbi Yisroel Reisman’s excellent “Pathways of the Prophets” ppg. 272 - 311, who expounds upon practical examples of understanding calendar calculations at length. The Chazon Ish (O.C. 138, 4) writes that knowing the calculations for the Lunar month are considered Torah.

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