In the Yeshiva where I teach, one of my students came to me rather incredulously- "I heard that the Tenth of Teiveis falls on a Friday this year—but I thought that we cannot have fast days on a Friday? I don’t remember a fast ever falling on Friday!"
Although Moshe’s halachic assumption is inaccurate, it is easy to comprehend why he made this mistake. In our current fixed calendar, the only fast day that ever falls on a Friday is Asarah BeTeiveis. And the last time this happened was exactly ten years ago, before he was old enough to fast.
There is another, more sophisticated, basis for Moshe’s question. In a "regular" (kesidrah) year Marcheshvan (usually, but inaccurately called simply "Marcheshvan") contains 29 days and Kislev 30. In such a year, Asarah BeTeiveis always falls on the same day of the week as Rosh Hashanah. And, since Rosh Hashanah cannot fall on a Friday, one might think that Asarah BeTeiveis should not fall on Friday either.
However, our fixed calendar system has fourteen "types of years," seven leap years, and seven common years. Of those fourteen "types of years," four of them result in Asarah BeTeiveis falling on Friday, two of them in a leap year and two in a common year. This is because if Rosh Hashanah falls on Thursday and the year must have a day added (sheleimah), (I explain this concept in a different article which I will be sending in one of the nearcoming weeks) the day added is the 30th of MarMarcheshvan, which postpones Asarah BeTeiveis to a day later in the week – to Friday. In addition, if Rosh Hashanah falls on Shabbos and the year must have a day deleted (chaseirah), the day subtracted is the 30th of Kislev, which moves Asarah BeTeiveis forward one day in the week – again to Friday. Since both of these scenarios can happen in either a normal year or in a leap year, there are four different "years" that result in Asarah BeTeiveis falling on Friday.
This year provides an example. Rosh Hashanah fell on Thursday and the year is sheleimah, meaning that both Marcheshvan and Kislev have 30 days, which avoids Rosh Hashanah from falling next year on Wednesday. But adding the 30th day to Marcheshvan causes Asarah BeTeiveis to fall on Friday. This type of year is referred to as a השג year, theה standing for Thursday (the fifth day of the week), the day of Rosh Hashanah; the ש for sheleimah, and the ג for the day of week that Pesach will fall this year, which is Tuesday, the third day of the week, which result because this is a leap year.
(By the way, the year 5774, which occurs in three years, is also a השג year exactly as this year is, so remember not to throw away your Hebrew calendar at the end of the year; you can reuse it in three years. On the other hand, the molad times will be different, as will the times for zman keriyas shma [which is dependent on the solar calendar], so maybe that is not such a good idea. Good thing for the calendar makers.)
If we plan a bit ahead, we will discover that all four types of years when Asarah BeTeiveis falls on Friday will occur within the next few years. The year 5781 (the end of the secular year 2020), is a common year in which Rosh Hashanah falls on Shabbos. Both Marcheshvan and Kislev are 29 days that year, which results that the last day of Chanukah that year is a Friday, the 3rd of Teiveis, and the fast of Asarah BeTeiveis falls on the following Friday.
BACK TO BACK FASTS
If we look ahead to the Hebrew calendar years 5784 and 5785, corresponding roughly to the secular years 2023 through 2025, we discover the fairly unusual situation of having back-to-back years with Asarah BeTeiveis falling on Friday both in 5784 (2023) and in 5785, (when it falls on January 10, 2025), each for a different reason: In 5784, which is a leap year, Rosh Hashanah falls on Shabbos and it is a chaseirah since both Marcheshvan and Kislev have 29 days, thus causing Asarah BeTeiveis to occur one day earlier in the week than Rosh Hashanah – Friday. 5785 is a common year when Rosh Hashanah falls on Thursday and it is a sheleimah when both Marcheshvan and Kislev have 30 days. Of course, I’m sure you noticed that there is no Asarah BeTeiveis in the secular year 2024, but it falls out twice in 2025. I will explain this phenomenon shortly.
A rocket scientist once attempted to explain to me why Asarah BeTeiveis falls occasionally consecutively on Friday. I am going to attempt to explain what he told me. When Rosh Hashanah in a leap year falls on Shabbos, that year cannot be a regular leap year of 384 days, because that would cause the next Rosh Hashanah to fall on Friday, violating the rule of lo adu Rosh, since this would result in Yom Kippur falling on Sunday. To avoid this happening, that year must either be shortened by a day (chaseirah), moving the next Rosh Hashanah forward to Thursday, or by adding a day (sheleimah), pushing the next Rosh Hashanah to Shabbos. Which of these happens is dependent on when the molad of the new moon for the next Rosh Hashanah falls. But if the year is indeed chaseirah, the loss of the day moves Asarah BeTeiveis to Friday, a day earlier in the week than was Rosh Hashanah.
Now then: When the year is made chaseirah (and Rosh Hashanah of the second year falls on Thursday as a result), it sometimes results that the second year requires an extra day to avoid the following year’s molad from falling too early. What has basically transpired is that because one year was shortened by a day, the next year requires a compensation of an additional day. When this happens, both Marcheshvan and Kislev in the second year now have 30 days. This results in Asarah BeTeiveis in the second year being postponed from Thursday to Friday.
If I understood the rocket scientist correctly, the only way this phenomenon of Asarah BeTeiveis falling in two consecutive years on a Friday is when the first year is a leap year that begins on Shabbos that was chaseirah and the second year is a common sheleimah year that begins on Thursday. Every time I have found this on the calendar it has been such a phenomenon, but I take no responsibility for ascertaining that this is the only way this can happen. I make no claim to be a rocket scientist.
What did Teddy Roosevelt and Richard Nixon have uniquely in common?
The last time Asarah BeTeiveis fell in two consecutive years on Fridays was in 5733 (on December 15, 1972, when Richard Nixon was president) and 5734 (on January 4, 1974). Few of those reading this article were fasting the previous time that Asarah BeTeiveis occurred on Friday in back-to-back years since this was on December 20, 1901 and January 9, 1903. Teddy Roosevelt was president, having succeeded to the office when William McKinley succumbed on September 14, 1901, to the wounds inflicted by Leon Frank Czolgosz. According to my research, these were the only two times the phenomenon of Asarah BeTeiveis falling in two consecutive years on Fridays occurred in the Twentieth Century. Is there any significance to the fact that both Roosevelt and Nixon were Republicans? Let us wait eagerly to see who wins the election of 2020 to see who will be president in 2023 and on January 10, 2025, the next back-to-back Asarah BeTeiveis on Friday. Perhaps the Republicans can keep this streak running!
The wait for the next back-to-back Friday Asarah BeTeiveis observances after 2023 and 2025 is not quite as long. Someone planning on good health and longevity can look forward to fasting on two Fridays of Asarah BeTeiveis in the years 5831 (on December 12, 2070) and 5832 (January 1, 2072), providing an auspicious way to celebrate the secular New Year.
By now, you presumably have noted that the secular years 1902 and 1973 both missed having Asarah BeTeiveis, and that so will 2024 and 2071. That a secular year misses Asarah BeTeiveis is not particularly significant. Almost every halachic leap year causes the pushing of Asarah BeTeiveis into the next secular year, and means that Asarah BeTeiveis misses one secular year, and falls out in January and then December of the year following. As a result, seven of nineteen secular years miss out on Asarah BeTeiveis. (Actually, it is slightly less, since about twice a century Asarah BeTeiveis in a leap year falls on December 30 or 31.)
COINCIDENCE OR DELIBERATE
Although it would appear that the reason no other fast occurs on a Friday is simply a coincidence of the fixed calendar, one early authority contends that observing Asarah BeTeiveis on Friday has a Tanach basis and deep halachic significance. The Avudraham explains that since the verse in Yechezkel (24:2) identifies the Tenth of Teiveis as etzem hayom hazeh, this very day, these words require that Asarah BeTeiveis be observed on the date that it occurs and may not be moved. The Avudraham expressly states that if Asarah BeTeiveis were to fall on Shabbos, we would be required to fast on Shabbos just as we are required to fast when it falls on a Friday. This means that prior to the establishing of our calendar by Hillel Hasheini, whenever Asarah BeTeiveis fell on Shabbos (during the period after the Churban), Klal Yisrael fasted on Shabbos, similar to the fasting we do when Yom Kippur falls on Shabbos! This ruling of the Avudraham seems unusual – particularly, since there is no record in the Gemara of such a halacha.
We can easily understand why the Beis Yosef (Orach Chayim 550) takes strong issue with Avudraham’s approach, and questions why one should treat Asarah BeTeiveis more strictly than any other rabbinically ordained fast. In addition, Avudraham’s position conflicts both with Rashi (Megillah 5a s.v. aval) and the Rambam (Hilchos Taanis 5:5), both of whom mention that when Asarah BeTeiveis occurs on Shabbos, the fast is postponed to Sunday.
Nevertheless, we must understand the conceptual basis why the Avudraham understands Asarah BeTeiveis to be a stricter fast than the others. It would seem that its significance is because it is the beginning of the tragedies that resulted in the churban, a message we should take to heart when we observe this fast, whether or not it occurs on Friday.