Laws relating to a Leap Year

* This article is an excerpt from the above Sefer

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Laws relating to a Leap Year

1. The reason behind leap years:[1]

Although the Jewish month and year is lunar based, the Jewish year is occasionally amended with an extra month in order so it be in sync with the solar year and its seasons. The reason this is necessary is because the lunar year of 12 lunar cycles consists of between 10 to 12 days less than the annual solar cycle [Lunar cycle is between 352-354 days, while the solar cycle is 364 days] which would mean that every year the Jewish calendar would become 10 to 12 days behind the solar one, eventually causing the holidays to fall during any season, such as having the holiday of Passover in the early winter or late summer. [In contrast, the Muslim calendar which is completely lunar based can have its holidays fall by all seasons of the year.] Due to this and other reasons, periodic leap years were established in order to have an extra month added to the year and hence catch up to the yearly deficit of days that are incurred in the lunar calendar versus that of the solar. This is necessary, as the Torah[2] commands us to guard the month of “Aviv” and make the Pesach, which alludes to the necessity of arranging for the Aviv/spring and Pesach holiday to always coincide.[3]


2. The Mazal of Adar in a leap year:[4]

The Mazal of Adar is the constellation of “Dagim/fish” and corresponds to the tribe of Yosef. Being that Yosef bore two of the tribes, Menasheh and Efraim, therefore his corresponding Mazal month occasionally contains two months, two Adar’s, and is hinted to in the plural use of the Mazal of “Dagim” as opposed to “Dag.” Thus, Adar Sheiyni does not contain a unique Mazal and is rather included within the Mazal of Adar Rishon.


3. Marbim Besimcha-During a leap year does the Mitzvah to increase in joy apply in both months of Adar?

Some Poskim[5] write the Mitzvah to increase in joy only applies to Adar Sheiyni, however in Adar Rishon the Mitzvah does not apply. However, the Rebbe[6], after analyzing this subject, concludes that the Mitzvah to increase in joy applies also in Adar Rishon.[7]


4. In which months does one celebrate Purim?[8]

During a leap year, Purim is celebrated in the second Adar. The reason for this is because we desire to proximate the Purim salvation to the redemption from Egypt, the redemption of Mordechai to the redemption of Moshe. We do not celebrate Purim twice, as it is learned from a verse in Esther that we only celebrate Purim one time.

5. Leap years-Birthdays, Bar Mitzvahs and Yartzites:

*See Daily Halacha of 9th of Shevat for the full details of this matter!

Birthdays and Bar-Mitzvas are celebrated in the second Adar, unless one was born in Adar I. Some have received a directive from the Rebbe to celebrate the birthday twice, in Adar I and Adar II. One commemorates a Yartzite in the first Adar unless the person passed away in Adar II. [Some are stringent to commemorate the Yartzite also in the second Adar.]

6. Moshe’s birthday and Yartzite on a leap year:

Coming up! 

7. The Chevra Kadisha fast:[9]

The custom of Jerusalem, and other cities in Israel, is to fast on the 7th of Adar, which is the Yartzite of Moshe Rabbeinu.[10] [In a leap year, it is done on the 7th of Adar Sheiyni.[11] However, some communities fast in Adar Rishon[12], which is the date that Moshe’s Yartzite is commemorated during a leap year.[13]]


8. Annual commemoration of a miracle:[14]

One who annually commemorates a miracle that occurred to him in the month of Adar is to commemorate the miracle in Adar I, if the miracle occurred in the 1st Adar of a leap year. If it occurred on the second Adar of a leap year, then one commemorates it in Adar II of a leap year. If it the miracle took place in a year with one Adar, then in a leap year, some Poskim[15], rule that it is to be commemorated in the first Adar, while other Poskim[16] rule it is to be commemorated in the second Adar. The meal that takes place in commemoration of the event is considered a Seudas Mitzvah.[17]

9. Purim Katan:

Coming up!

10. Laws of mourning-Aveilus-The mourning period during a leap year:[18]

Even during a leap year, the period of Aveilus for a parent extends for only 12 months, and the two months of Adar are considered two out of the 12 months of mourning.[19] [As a result, one whose 12 months of mourning for a parent occurs during leap year months of Adar, will conclude his mourning customs a month prior to the first Yahrzeit. Thus, for example, if the death/burial was on the 13th of Tishrei of a leap year then the children’s last day of Aveilus is on the 12th of Elul.] Thus, after the passing of 12 months [which is one month before the Yahrzeit] he may participate in festive meals without restriction.


[1] Rambam Hilchos Kiddush Hachodesh 1:1-2, and Chapter 4; Encyclopedia Talmudic Erech “Aviv.”

[2] Devarim 16:1

[3] Mechilta Parshas Bo chapter 2; Sifri Parshas Rei

[4] See Kedushas Levi Parshas Shekalim-Tetzaveh

[5] Sheilas Yaavetz 2:88

[6] Likkutei Sichos 16 p. 344; Igros Kodesh Miluim [printed in Shulchan Menachem 3 p. 306]; Nitei Gavriel 11:1 based on Megillah 6b, Chasam Sofer O.C. 163, and all the old Luchos

[7] The reason: As we celebrate the birth of Moshe Rabbeinu in Adar Rishon, and it is this matter which motivated the law of increasing in joy during Adar. [Rebbe ibid] It is also supported from the fact the Mishneh in Megillah 6b does not list “joy” as one of the differences between Adar Rishon and Sheiyni. [Nitei Gavriel ibid]

[8] Megillah 6b; Levush brought in Kaf Hachaim 697:1; The first month of Adar is the added month and not the second. [Gemara Rosh Hashanah 19b; See Yerushalmi Megillah 1:5]

[9] See Nitei Gavriel Vol. 2 chapter 97-98

[10] See Nitei Gavriel Vol. 2 chapter 97 in length

[11] Nitei Gavriel 97:2 and footnote 4 in name of Sefarim

[12] See Nitei Gavriel ibid footnote 4

[13] Magen Avraham 580:8; Teshuvos Mahril 31; Terumos Hadeshen 244; Rama 568:7; Aruch Hashulchan 580:3; Mishneh Berurah 580:15; Orchos Chaim; Likkutei Sichos 16 p. 344 footnote 39: This is the final ruling, as the majority of Jewry lived in their provinces and testified this to be the custom.

Other Opinions: Some Poskim hold that during a leap year Moshe’s Yartzite is to be commemorated on Zayin Adar II. [Chacham Tzevi, brought in Sheilas Yaavetz 1:117; Siddur Yaavetz; Chasam Sofer 163; Vayaan Yitzchak 39].

[14] M”B 697:2

[15] Maharash Halevi 15; M”B 697:2 [unlike his ruling in 686:8, however see Nitei Gavriel 12 footnote 3]; Rivivos Efraim 4:171

[16] Chasam Sofer O.C. 163; M”B 686:8; Nitei Gavriel 12:3

[17] The reason: As every meal which takes place to commemorate G-d’s miracles and wonders has a status of a Mitzvah feast. [ibid; Chavos Yair 70; P”M 444 M”Z 9; Chayeh Adam 154:42 in name of Rashal Baba Kama 37;] This is unlike the ruling of the Peri Chadash 496.

[18] Michaber 391:2 regarding festive meals that “Even in a leap year he is permitted after 12 months” [See Nekudos Hakesef 391:1]; Rosh in name of Ravaya; Shach 391:2; 395:3; Taz 391:1 “All Aveilus ends after 12 months even in a leap year, and those that continue the mourning customs into the 13th month have no source and are certainly doing a worthless act”; Bach 391; Chochmas Adam 166:8; Kitzur SHU”A 216:3; Beis Yitzchak 2:157; Maharsham 3:205-8; Mateh Ephraim 3:3 regarding Kaddish; P”M 55 A”A 10 regarding Kaddish; Nitei Gavriel 34:4; Vol. 2 62:5

Other opinions: Some Poskim question that perhaps the extra month of a leap year is considered part of the 12 months, and hence one must also keep Aveilus in the 13th month, until the Yahrzeit. [See Beis Hillel 391; Nitei Gavriel ibid footnote 6 in name of Beis Lechem Yehuda and Chochmas Shlomo; Lechem Hapanim in Kitzur SHU”A 26:17; Beis Yitzchak ibid; Maharsham ibid; Mateh Ephraim ibid; P”M ibid]

[19] The reason: As nowhere do we find written that the Aveilus period extends for “a year” or “until the Yahrzeit” and rather in all areas it states “for 12 months.” [Beir Hagoleh ibid]

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