If you forgot to make an Eruv Tavshilin

Question

I recall hearing that if you forgot to make an Eruv Tavshilin there is a way to make it on the first day of Yom Tov. Does anyone know how this is done?

Answer 1

Shulchan Aruch (Orach Chaim 527:22) says that you should make the following declaration when making an Eruv on the first day of Yom Tov:

"If today is a Yom Tov, then I don't need an Eruv [because tomorrow is really a weekday, and I can prepare for Shabbos as usual]. But if today is a weekday, then with this Eruv I shall be allowed to bake, cook, ...."

Note the following caveats:

• This doesn't work for Rosh Hashanah, because its two days are halachically considered "one long day."

• According to one opinion cited in Shulchan Aruch there, this works only if you have some food already prepared from before Yom Tov. (Though Mishnah Berurah, ibid. :75, says that in practice we don't follow this opinion.)

• There are variant opinions as to whether to recite the blessing when making an Eruv with this condition (Mishnah Berurah ibid. :74).

Answer 2

Hirhurim just put up a post discussing both the first day solution and the rely-on-the-Rabbi solution.

Answer 3

This doesn't directly answer the question posed, but something to bear in mind is that one who lives in a community where the rabbi makes an eruv tavshilin including "ולכל בני ישראל הדרים בעיר הזאת" can rely on said rabbi's eruv if he forgot to make one himself — but not twice in a row (viz, not two occasions in a row for which he should have made an eruv: these will often not be consecutive holidays). (No source handy, sorry.)