Mishnah/Seder Nashim/Tractate Ketubot/Chapter 1/1
Seder Nashim, Tractate Ketubot: Chapter 1, Mishnah 1
A virgin gets betrothed on Wednesday and a widow on Thursday. (The reason a virgin gets married on Wednesday is because...) The Rabbinical Court meets twice a week, on Monday and on Thursday; and if he (the groom) wants to make a claim that she is not a virgin he can wake up early to go to the Court (on Thursday morning, to make his claim).
(see the next Mishnah for an explanation of why it matters if she is a virgin or not)