For those outside of Israel the requirement is for two days of yom tov (and sometimes Rosh Chodesh), originally due to uncertainty and now due to tradition. But we don't do this for all holidays even though they involve time-bound mitzvot:

  • Yom Kippur: it would be impractical to observe for two days; is that the reason or is it coincidence?

  • Chanukah: is the 25th of the month late enough that we are certain of the date?

  • Purim: I have no guess here

Is there a unifying reason for when we do and don't add the second day, and if so what is it? Or is it on case-by-case basis, and if so what are the reasons for these three cases?


3 Answers 3


You are right as to the reason why we don't have two days of Yom Kippur is because it is dangerous and we don't decree on people decrees that they can't handle.

As to the other two, see 9 Days of Chanukah?


Yom Kippur -- they realized that most people can't handle a 48-hr fast, so they didn't enact it.

Purim and Chanukah -- came much later in history, and aren't "no-work" holidays. Never mind they're entirely of post-Mosaic origins, which means we're more lenient with them in cases of doubt.

  • @ShmuelBrin You may want to read Rambam, Hilchot Kiddush Hachodesh. I think the 4th or 5th chapter discusses why Yom Tov was observed for 2 days during the time of Sanhedrin, and why we do it now. As this answer states, the main concern was the violation of melacha which doesn't apply to Chanukah and Purim. Contact me if you can't locate the relevant paragraphs in Ramba"m or if you still don't understand it.
    – DanF
    Aug 6, 2015 at 14:51

It's not necessary to keep 2 days for a holiday that is d'rabanan and that has no issur melacha.

  • 1
    Why not? [15ch]
    – Double AA
    Aug 6, 2015 at 14:22

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