### Trivia Quickie - Rosh Chodesh

Today is Rosh Chodesh - the first day of the Jewish month of Shevat. As we read in this coming week's Torah portion, sanctifying the new moon was the very first commandment given to the fledgling Jewish nation, while still in Egypt. More detail here if you're interested.

Since the outgoing month of Teves had 29 days, there is only one day of Rosh Chodesh this month. When the outgoing month has 30 days, two days are celebrated as Rosh Chodesh; the 30th day of the old month and the 1st day of the new. Under the current Jewish calendar system, the months generally alternate between 29 and 30 days, so the 1-day and 2-day types of Rosh Chodesh generally alternate every other month as well.

With that as background, my Torah-trivia quickie for today is: Is it possible to go as long as six months without a one-day Rosh Chodesh being observed, and if so, how?

Answer: Both David and Ezzie were on the right track. The key data point is that there are two months which can have either 30 or 29 days, Cheshvan and Kislev. However, what makes it easy to get confused is that if month N has two days of Rosh Chodesh, it's because month N - 1 had 30 days, not month N itself.

So with that, here is the solution:

Av: 1 day Rosh Chodesh (always)

Elul: 2 days Rosh Chodesh (always)

Tishrei: No Rosh Chodesh (has Rosh Hashanah instead!)

Cheshvan: 2 days Rosh Chodesh (always)

Kislev: 2 days Rosh Chodesh if Cheshvan has 30 days

Teves: 2 days Rosh Chodesh (most years)

Shevat: 1 day Rosh Chodesh, for the first time in six months

## 6 Comments:

Since you ask the question, the answer is obviously "yes."

IIRC Kislev, Teves and Shvat can be either 29 or 30 days. (chaser or malei.) So if all 3 of them are chaser, then we'd have Tishrei, Cheshvan is Chaser so it's 2 days; Kislev would be chaser (though it usually isn't); Teves would be chaser (as it usually is); Shvat would be chaser, though usually not. Finally Adar would have to be a regular year (Adar I is the leap month and is Malei.) and would be chaser.

Having all 3 of the above mentioned months be chaser, though, I'm sure is exceedingly rare.

David: You're close, but no (chocolate) cigar!

If there are no correct responses I'll post the answer tonight.

Rosh Chodesh

Av: 1 day.

Elul: 2 days.

Tishrei: None, Rosh Hashana.

Cheshvan: 2 days.

Kislev: Can be 2 days.

Teves: Usually 2 days.

Shvat: 1 day.

It makes sense, but I'm confused: I thought it was Kislev & Teves that can 29 or 30, not Cheshvan & Kislev.

Hmm.

Av: 30 days, so Elul is 2 day RC.

Elul: 29 days, but there's RH.

Tishrei, 30 days, so Cheshvan is 2 day RC.

Cheshvan 29 days, so Kislev should be 1 - no?!

I think I'm right, if there's an answer. But I'm still confused.

Yay! :)

Now, why did I always think it was Teves, not Cheshvan, that was interchangeable...?!

Elie,

I thought that a month has 2 days of Rosh Chodesh if it itself has 29 days. That way the first day of Rosh Chodesh, which is the last day of the previous month serves also as the 1st day of the new month giving it 30 days.

David, Ezzie:

Normally when the months alternate 29 and 30 days, a month with 29 days would start off with two days of Rosh Chodesh. But when there are two 30-day months in a row, as when Cheshvan has 30 days or when an Adar Rishon is added, then a 30-day month might also start off with a two day rosh chodesh, since the previous month also had 30 days.

Again, what makes this tricky/confusing is that the two days that are referred to as "Rosh Chodesh N" are actually the 30th of month N-1 and the 1st of month N.

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