Today (23 March 2020) Israel's Supreme Court rejected a petition to declare this year a leap year so Pessah can be postponed for a month, and the seders don't have to occur during a lockdown (hopefully!).

I don't know why the petitioners went to a secular court, but do the rabbis have the authority to declare a leap year under the circumstances?

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    Do you mean rabbis nowadays when we have a fixed calendar? Or does your question apply even before the fixed calendar? In other words, would you be interested in an answer that says that a leap year could be declared for practical reasons prior to the establishment of our fixed calendar?
    – Daniel
    Mar 23, 2020 at 14:43
  • I am talking about TODAY. Mar 23, 2020 at 14:46
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    Aside from the Sanhedrin issue (which is absolutely the answer), wouldn't the year have to have been declared before Rosh Chodesh Adar - i.e., even if this were done last week (before Mevorchim Hachodesh which publicly (or privately this time...) announced Rosh Chodesh Nissan), it would still have been after Parashas Zachor, Purim, etc. that all are in "Adar II" when there is a leap year. Mar 24, 2020 at 17:15
  • @manassehkatz-Moving2Codidact No, that's not a problem. If the leap year is declared after Purim it is simply celebrated again. It does have to be done before Nissan begins.
    – Double AA
    Mar 27, 2020 at 18:09

2 Answers 2


There are two problems, both are discussed (among others) in Sanhedrin 11a. The first is that you need a Sanhedrin with a Nasi to intercalate a year. The second is that there are certain reasons for intercalating a year (e.g. damaged roads and bridges to Jerusalem, ripening of the grain and fruits). Actually, one of the reasons for introducing a calculated calendar was to avoid the dependence on the Sanhedrin, which was vulnerable of being disbanded by the oppressors. As Rambam says (Hilkhot Kiddush haChodesh 5:2–3):

וּבִזְמַן שֶׁאֵין שָׁם סַנְהֶדְרִין קוֹבְעִין עַל פִּי הַחֶשְׁבּוֹן הַזֶּה שֶׁאָנוּ מְחַשְּׁבִין בּוֹ הַיּוֹם וְאֵין נִזְקָקִין לִרְאִיָּה. (...) וּמֵאֵימָתַי הִתְחִילוּ כָּל יִשְׂרָאֵל לְחַשֵּׁב בְּחֶשְׁבּוֹן זֶה. מִסּוֹף חַכְמֵי הַגְּמָרָא בְּעֵת שֶׁחָרְבָה אֶרֶץ יִשְׂרָאֵל וְלֹא נִשְׁאַר שָׁם בֵּית דִּין קָבוּעַ.‏

When there is no Sanhedrin, the monthly calendar is established according to the fixed calendar that we follow now, and the sighting of the moon is of no consequence. (...) When did the entire Jewish people begin using this calendar? At the conclusion of the Talmudic period, when Eretz Yisrael was in ruin, and an established court no longer remained there.

So current rabbis would only have authority to intercalate a year if they formed a new Sanhedrin and the aforementioned criteria from the Talmud would hold.

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    If there was a Sanhedrin, would the pandemic be considered a kosher reason to add a month to the year? Mar 23, 2020 at 19:20
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    @Daniel Based on the gemara, I think for that we would need a Temple, because if pilgrims had unforeseen delays, they could intercalate. But by the Third Temple all Jews will return to Israel and there won't be such epidemics either, right? Mar 23, 2020 at 20:12
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    @Kazi Depends on if the Rambam or Ramban is correct, which ultimately goes back to Rav Chanina and Shmuel. אין בין עולם הזה לעולם הבא אלא שעבוד מלכיות בלבד – according to the Rambam, there will still be poverty, famine, and yes, illness even after Mashiach comes; the only difference is that we'll have autonomy to serve Hashem properly. Your position reflects that of Ramban and/or Rav Chanina (it's complicated how he learns that Gemara).
    – DonielF
    Mar 25, 2020 at 17:48

The rabbis currently do not have the authority to declare a leap year because there is no Sanhedrin.

The current calendar was set up by Hillel II and is completely fixed by calculation. Indeed, even though the current calendar does have an error of one day in 216 years, we cannot fix that until the Mashiach comes and a new Sanhedrin appointed.

As we can see:

As a remedy, the Sanhedrin instituted the Hillel II calendar in 4119 AM -359 CE. In one sense it preserved uniformity among Jewish people abroad, but in another way it severed ties between Israel and the Diaspora.

The calendar itself, in general, is quite accurate, averaging 29.5 days per month and 365.2468 days per year (compared to the average solar year length of 365.2422). It allows for adding and subtracting a day in consecutive years as needed, so as to avoid waving the lulav on Shabbat, or landing Yom Kippur adjacent to a Shabbat.

Implementing the Hillel II calendar was the Sanhedrin’s last big decision before disbanding. Whenever the Hillel II calendar will be decommissioned in the future to return to sighting and declaring the New Moon days, it would have to be at the authority of a reconvened Sanhedrin.

  • Isn't there a teaching that under extraordinary circumstances the rabbis can suspend established laws and rule as needed? Mar 23, 2020 at 14:42
  • @Maurice depending on the exigency different rules can and can't be suspended. So what?
    – Double AA
    Mar 23, 2020 at 15:07
  • It's one thing that we don't have Sanhedrin, but there are other issues as well. judaism.stackexchange.com/a/112178/15256 Mar 23, 2020 at 15:37
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    I know you're quoting from that article, but "so as to avoid waving the lulav on Shabbat" is incorrect. It should say so as to avoid hoshana rabbah falling in Shabbat
    – robev
    Mar 23, 2020 at 16:20
  • One of the better calendars uses a 353 year cycle. The next year divisible by 353 is 6001. Perfect timing for the Mashiach to fix the calendar.
    – CashCow
    Mar 26, 2020 at 16:54

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