You need to write the time in your divorce certificate (this document is written when you when married not when you get divorced). If you have a divorce certificate without a time then you can't get married. If you get married then you don't undo it, even if you don't have children.
If it was dated early, or if it was written during the day and signed the night after, it is invalid, even if they were discussing that matter. And there are those who say that if it is written during the day and signed the night after, in times of distress, it is valid. Hagah: And an early-dated get, even though it is invalid, if another man betroths her, she needs a get from the second, and she may not return to the first (Piskei Mahari, siman 13, according to the Rambam, and Bet Yosef in the name of the Ran and the Rashba).
If it was written during the day and they didn't have time to sign it until night, if they wrote in it before the signing: This get was written on such-and-such a day and the witnesses did not have a chance to sign it until night, and the witnesses sign after, it is valid.
One who sends a get from place to place, even if he dates it early, for they write the time from the day on which it is written and it won't get there until later, this is valid, for it has a voice [people know about it].
A get which was not delivered on the day it was written, there is no remedy to validate it, except to send it through an agent. Hagah: However, we are accustomed to act stringently and to write another (thus it seems from the words of R. Peretz, cited in Orhot Hayyim). And a get that a woman has possession of, we assume that it was given to her on the day it was written, and she need not bring proof, unless something happened to it, such as it was cast away (Tur and Tosafot, and the Rosh).
If he told two to write a get and to sign it and give it to his wife, and the matter was delayed for a day or two, or the get was found to be nullified and they had to write another get, when they write the time and place, they do not write the time that the husband told them to write it, nor the place. How so? If they were in Jerusalem when the husband told them, and it was Tishrei, and it was delayed until Nisan, and by then they were in Lod, they write the time from Nisan and [the place] Lod.
A get on which he did not write the name of the day, rather [he wrote] in the first or second week of a certain month, or in a certain month, or in a certain year and did not mention the month, [or] even if he wrote in a certain week, it is valid. And so if he wrote on it: Today I divorced her, it is valid, for the meaning is this day on which the get was issued.
If he wrote the time in it, cut the time out of it, and then gave it to her, it is valid. And there are those who invalidate.
A get whose "time" is late (in the future), it's valid to divorce with it. And even if he gives it to her immediately, the divorce is not affected until after the time that's written in [the get]. And some invalidate a future get.
If the scribe skipped [the words]: "according to the creation of the world", it's valid.
If he skipped the "thousands" and the "hundreds", only that he wrote "such and such" specifically, it's valid. And even if he also skipped "the creation of the world."
If he skipped "five" and only wrote "thousands", it's valid.
If he wrote the general and the small detail, and skipped the middle detail, e.g. he wrote "Five-thousand and 17" and skipped the "three hundred," it's invalid. And if she [re]marries, she shouldn't leave. And there is someone who says that we require of her a valid get from her first husband, and she remains unde the second [husband].