This column is dedicated to the refuah sheleimah of Shlomo Eliezer ben Chaya Sarah Elka.
In this week’s parshah the Torah lists the different korbanos that we are to bring on the various different days of the year. In perek 28, pasuk 11 the Torah commands us as to which korbanos we must bring on Rosh Chodesh. In the times of the Beis HaMikdash, Rosh Chodesh was determined by the actual birth of the moon. Witnesses would testify before beis din that they saw the rebirth of the new moon, and beis din would pronounce that that day was Rosh Chodesh. Nowadays, when there is no beis din to pronounce Rosh Chodesh, we have a calendar with all the dates of Rosh Chodesh predetermined. Certain months have two days of Rosh Chodesh, and others have only one. Whenever a month has two days that are observed as Rosh Chodesh the first day of Rosh Chodesh is the last day of the previous month, and the second day is the first day of the new month.
The Birkei Yosef (Orach Chaim 427:1) quotes a manuscript of the Tosfos Rid. The Tosfos Rid was asked why we have two days of Rosh Chodesh. He explained that it was not because we are unsure of the correct day but rather because a lunar month actually consists of 29 and a half days. Therefore the 30th day should be divided in half – split evenly between the previous month and the new month. But since we cannot split a day in half, the calendar was arranged so that several months will be full (30 days) and others will be shorter (29 days). Thus, in essence, every 30th day should be Rosh Chodesh. Nevertheless, since the Chachamim instituted that the 30th day should belong to the previous month, both the 30th and the 31st days are Rosh Chodesh.
Several Rishonim say that even in the times of the nevi’im two days of Rosh Chodesh were observed. The Smag (assei 47) says in the name of his rebbe, Rabbeinu Mishulem, that the pesukim by Dovid HaMelech imply that two days of Rosh Chodesh were observed. The Rambam (Hilchos Kiddush Hachodesh 8:4) says that the 30th day is always observed as Rosh Chodesh, whether there are one or two days of Rosh Chodesh that month. The Shibolei Haleket (168) also says that even in the times of the nevi’im, two days of Rosh Chodesh were observed.
The Tashbatz (volume 1:153) writes that the reason why Rosh Chodesh is sometimes two days, even though today we know the exact time of when things should be, is because our forefathers were unsure and thus kept two days. We follow their minhag even though we know for sure.
There is much discussion regarding one who is born or niftar on the first day of Rosh Chodesh, the 30th day of the month, over how to act concerning other years in which that month only consists of 29 days. This occurs in the months of Cheshvan, Kislev, and Adar.
Rav Moshe Feinstein (Igros Moshe, Yoreh De’ah 3:159:3,4) discusses which day a child observes yahrzeit if the parent died on the 30th day of Cheshvan or Kislev – but in future years those months do not have 30 days. He says the child should observe on the first day of the next month. (The other option would be to observe the yahrzeit on the 29th day of the month.) Rav Moshe argues that this day (the 29th day of the month) should not be observed as a yahrzeit since the parent was still alive on that day. On the other hand, the parent was no longer alive on the first day of the next month.
The Magen Avraham (568:7) says that if in the first year after the parent’s death the month also had 30 days, it is then established that the yahrzeit should forever be on Rosh Chodesh. Thereafter, if there are only 29 days in that month, the yahrzeit should be observed on the 29th day. This is because the parent died in either Cheshvan or Kislev, not in the following month.
The Taz there argues that when there is no 30thday in the month that the parent died, yahrzeit should always be observed on the 29th day of that month, regardless of whether or not the first year after the death had 30 days. Rav Moshe explains that the reason why one would observe yahrzeit on the first day of the next month is because since the 30th day is called Rosh Chodesh for the next month, we can consider as if the parent died on Rosh Chodesh. Therefore, the yahrzeit should be observed on that Rosh Chodesh. And when there is two days of Rosh Chodesh the yahrzeit is observed on the first day, since that is the day when the parent actually died. When there is only one day of Rosh Chodesh, that day should be observed – even though it is technically a different month. Why? Because they are both called Rosh Chodesh.