5785 - The Rarest Year of Them All Part IV « Insights into Halacha « Ohr Somayach

Insights into Halacha

For the week ending 21 December 2024 / 20 Kislev 5785

5785 - The Rarest Year of Them All Part IV

by Rabbi Yehuda Spitz
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As detailed in previous installments in our series, our current year, 5785, is not only a rare one, but calendarically speaking, actually the hands-downrarest of them all. 5785 is classified as a HaSh”A year in our calendars. This abbreviation is referring to Rosh Hashana falling out on Thursday (hei), both months of Cheshvan and Kislev being shalem (shin - 30 day months instead of possibly 29; these are the only months that can switch off in our set calendar), and Pesach falling out on Sunday (aleph).

A HaSh”A year is the rarest of years, and out of the 14 possibilities in Tur’s 247-year calendar cycle, this year type occurs on average only once in about 30.19 years (approximately 3.3 percent of the time). Indeed, at times there are 71 years (!) in between HaSh”A years. The last time this year type occurred was 31 years ago in 5754 / 1994. The next time will be 20 years hence in 5805 / 2044. The next several times after that are slated to be 27 years further, in 5832 / 2071 and then a 51 year gap in 5883 / 2122.

The reasons and rules governing the whys and whens this transpires are too complicated for this discussion; suffice to say that when the Mishnah Berurah discusses these issues he writes “ain kan makom l’ha’arich,” that this is not the place to expound in detail, which is certainly good enough for this author.

Obviously, such a rare calendar year will contain many rare occurrences. This series article sets out to detail many of them. Perhaps as we get nearer to the actual events, we will discuss them in greater detail. Let’s continue on our journey through our unique year.

Cheshvan – Kislev Calculations

In Part Three we explained the significance of Cheshvan and Kislev both being shaleim this year. As noted, these months are the only months that can either have 29 or 30 days depending on the year. Some years both are chaseirim (‘missing’; meaning 29 day months); other years both are malei’im (‘full’; meaning 30 day months), and others Cheshvan is chaseir and Kislev malei. What is a given, is that this is one of the changing variables in our set calendar. As mentioned previously, in 5785 both months are malei – making this a shaleim year.

Skip the Birthday

This detail actually had interesting, and quite dramatic, ramifications this year, especially as pertains to Bar Mitzvah bachurim. You see, if a boy was born on the 30th of Cheshvan - which is also the first day of Rosh Chodesh Kislev, in a year that Cheshvan was malei, and in his Bar Mitzvah year Cheshvan is a chaseir, meaning there is no 30th of the month, our little lad does not become a man until the 1st of Kislev. In other words, he does not truly have a birthday, as in that year, his birthdate simply does not exist. Hence, his birthday is skipped and is pushed off one day until the next month. He may have been born in Cheshvan, but his Bar Mitzvah will assuredly be observed in Kislev.

The reason for this is that halachically one cannot become truly a Bar Mitzvah until he completes 13 entire years. 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 the one-day Rosh Chodesh Kislev, a.k.a. Alef Kislev.

Bar Mitzvah-ed a Day Early

Yet, it is when the flip side of this equation occurs when it gets real interesting. The Elyah Rabba, based on a ruling of the Bach, maintains that if a boy is born on the 1st of Kislev in a year when Cheshvan only had 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.

This fascinating, albeit relatively obscure psak of becoming a Bar Mitzvah one day before the birthday, is actually cited as halacha by the consensus of many great Acharonim, and codified as halacha by the Mishnah Berurah. In fact, it is due to this reason that the great Bobover Rebbe, Rav Shlomo Halberstam 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.

The same fascinating occurrence happened this year. Thirteen years ago, in 5772, Rosh Chodesh Kislev was a one-day Rosh Chodesh, as Cheshvan that year was chaseir. Yet, this year, 5785, as mentioned previously, both Cheshvan and Kislev are malei. Ergo, Rosh Chodesh Kislev is a two-day Rosh Chodesh. That means that a boy who was born on 1 Kislev 13 years ago (the singular one-day Rosh Chodesh Kislev that year), actually became Bar Mitzvah this year on Lamed Cheshvan, the first day of Rosh Chodesh Kislev, or, in other words, one day prior to his actual birthday!

In other words, to put a bit differently, on Monday, the first of Kislev, 5775 there were no Bar Mitzvahs at all – as anyone born thirteen years prior would have been observing his Bar Mitzva on the previous day! Fascinating, no? Just another noteworthy feature of our exceptional year.

No Early Yahrtzeit

However, it is important to note that according to the halachic consensus, this rule does not actually apply regarding Yahrtzeits, as a Yahrtzeit is strictly observed on the exact date when someone is niftar. Moreover, as Yahrtzeit observance is technically considered a neder (vow), the rule of thumb is that regarding nedarim, its observance follows the common vernacular. As Lashon Bnei Adam is to refer to the 1st of Kislev as Rosh Chodesh Kislev, that is the date that must be observed as proper Yahrtzeit, regardless of the month’s makeup.

Hence, in our current year, a Yahrtzeit for someone who was niftar 13 years ago on 1 Kislev (which, back in 5772 was a one-day Rosh Chodesh Kislev), would still have been observed this year on 1 Kislev, even though this year it actually ended up being the second day of Rosh Chodesh Kislev.

This maxim is in contrast to Bar Mitzvahs, as a child becomes Bar Mitzvah on the day he completes 13 full years. In other words, and as diverging from Yahrtzeit observance, the upshot of this discussion is that a Bar Mitzvah technically does not necessarily have to occur exactly on the boy’s actual birthday, as is showcased with a Rosh Chodesh Kislev Bar Mitzvah on this rare year.

Our fascinating journey detailing the many remarkable facets of our rare year will IY”H be continued…

Rav Samson Raphael Hirsch famously wrote that “the Jew’s catechism is his calendar.” It is this author’s wish that by showcasing the uniqueness of our calendar year and its rare minhagim, this series will help raise appreciation of them and our fascinating calendarical customs.

This author wishes to thank R’ Yosef Yehuda Weber, author of ‘Understanding the Jewish Calendar,’ for being a fount of calendarical knowledge and for his assistance with this series.


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.

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