Suppose I have a meeting, a court hearing, or any event that is set by some authority at a specific time in the future. Is there a word for such a "due date"? I don't mean a deadline (see the separate question for deadlines) by which something must be done, but a date or time at which something must be done.
Also die constituto, as in Sallust, Bellum Iugurthinum 13.9:
igitur ubi legati satis confidunt, die constituto senatus utrisque datur.
A quick look in Lewis & Short shows numerous examples of the idiom diem constituere from Caesar, Sallust, Terence, and others.
Die praescripta should do it. I'm told that it is a bit of legal Latin in England. (The opposite is sine die, without a day, sc. until an indefinite date.)
I've tended to use diēs indictus, which I got from Livy:
Et apparebat nihil liberae consultationis concilio quod in diem posterum indictum erat Boeotis relictum esse. (33.1)
Hac quoque gente adiuncta Chalcidem regressus, praemissis inde litteris, ut Demetriadem conuenirent principes Aetolorum, cum quibus de summa rerum deliberaret, nauibus eo ad diem indictum concilio uenit. (36.6)
Glancing through the corpus at PHI, though, it looks like diēs cōnstitūtus, as offered by cnread, is more common.