daf bit: Nedarim 76

A man can anul his wife's vow on the day he learns of the vow, but not later. What is meant by "day"? The mishna teaches: this means a calendar day, not 24 hours. If she vowed on the night of Shabbat, he can anul that night or the following day; if she vowed just before nightfall, he can anul only until nightfall. (76b)

(The biggest surprise to me was that one can anul a vow on Shabbat at all. There is a discussion of this on 76-77.)

(Email post; I couldn't get to the LJ web site this morning.)