What is the law if a Kesuba was written and signed during the day, before sunset, but the Chuppah took place at night?
If the Kesuba was written and signed during the day, and the Kinyan with the Chasan likewise took place during the day, then the Kesuba is valid even if the Chupa only took place at night, or several days afterwards. Furthermore, one may even initially do so, and so is the Chabad custom. However some Poskim rule that if the Kesuba was written by day and the Chuppah took place at night then the Kesuba is invalid and a new Kesuba must be written.
 See Beis Shmuel 66/7; Gittin 18a; Kochav Meyaakov 196Kaneh Bosem 2/1; Nitei Gavriel 31/10; Rebbe in Toras Menachem 10/199 [printed in Shulchan Menachem 6/44]; Poskim brought in Shulchan Menachem ibid
 Rebbe ibid
 Igros Moshe Even Haezer 4/105; Divros Mosh 290 footnote 54
 The reason: As the Kiddushin must take place in order for there to be a Shibud, legal binding, of the Kesuba, and since the Kedushin only took place at night it ends up the Kesuba was not legally bound until nighttime. Now, this is a problem being that the date of the Kesuba states the date of the previous day, and hence it is invalid due to it being a “Shtar Mukdam”, a predated document which is invalid due to its potential illegal ramifications towards liens. [ibid]