- Question: [Monday 2nd Teves 5782]
This past Shabbos, which was the 30th day of Kisleiv, we Baruch Hashem had a baby boy. I am wondering when this boy will celebrate his birthday in future years when there isn’t 30th day in Kisleiv.
In years that there is no 30th day of Kislev, and hence Rosh Chodesh Teves is only one day, he is to celebrate his birthday on the 1st of Teves. However, the Rebbe once gave an answer in such a situation for one to celebrate his birthday on both days, the 29th of the month of Kislev and on Rosh Chodesh Teves.
Explanation: As is known, the months of Cheshvan and Kislev, in contrast to other months of the year, are able to be either Malei or Chaser, either 30 day months or 29 day months, depending on the year. Accordingly, it one who was born on the 30th of Kislev will have years in which there is no 30th of Kislev, and the question is thus raised regarding when he should celebrate his birthday in such years. Should he celebrate on the 29th of Kislev, being that he was born in the month of Kislev, or should we celebrate on the first of Teves, being that he was born on the first day of Rosh Chodesh Teves. Now, while the annual date of one’s birthday is not really a relevant question discussed in halachic literature, being that in Halacha we don’t find the concept of an annual birthday, nonetheless, it is discussed regarding the question of when a child becomes Bar/Bas Mitzvah, and from there we can learn regarding the annual birthday as well. So Admur and other earlier Achronim discuss this question regarding the month of Cheshvan if the bar mitzvah boy was born on the 30th of Cheshvan and in his 13th year there is only 29 days in the month of Cheshvan. They rule that in such a case he is to celebrate his bar mitzvah on the first of Kislev. The reason for this is because just as originally, he was only born after a full 29 days passed from Mar Cheshvan, so too in his 13th year he must wait for 29 days to pass in the month of Cheshvan to become bar mitzvah, and hence his bar mitzvah is automatically delayed until the first of Kislev. Now while the similar case of one who was born on the 30th of Kislev is not discussed in the above sources, the Achronim conclude that in truth the same law applies, and hence one who was born on the 30th of Kislev is to celebrate his bar mitzvah, and consequently celebrate his birthday, on the first of Teves in any year in which there is in the 30th of Kislev. Despite this ruling, it is recorded that the Rebbe once gave an answer to an individual in the above situation for him to celebrate his birthday on both days, the 29th of the month of Kislev and on Rosh Chodesh Teves.
Sources: See regarding the 30th of Cheshvan: Admur 55:13; M”A 55:10; Elya Raba 55:9; Yad Ahron; M”B 55:45; Ketzos Hashulchan 15:6; Derech Hachaim; Kneses Hagedola; Poskim in Kaf Hachaim 55:60; This same rule applies regarding the 30th of Kislev: Elya Raba 55:9; P”M 55 A”A 10; Machatzis Hashekel 55:10; Tehila Ledavid 55:8; Kaf Hachaim 55:60; See regarding the Rebbes reply: Heichal Menachem 2:38-9; See regarding the Malei/Chaser months of Cheshvan and Kislev: Rambam Kiddush Hachodesh 8:5-6; Tur 428; Understanding the Jewish calendar chapter 12-13; Our Sefer “The laws & Customs of Rosh Chodesh” Chapter 2 Halacha 5E