CTFd was originally designed to be used in time-boxed situations where users can only access the competition content during specific times. CTFd has four time settings: Start Time, End Time, Freeze Time, and pausing the competition.
Start Time defines when the competition should begin and all competition content should be accessible.
End Time defines when the competition should end and all competition content should be inaccessible.
Freeze Time allows the competition organizer to specify a time where scores will be "frozen" to. Meaning that all submissions after Freeze Time will be recorded however the solves will not be shown to other users. The original purpose for this feature is to hide competition scores in order to generate suspense for a final reveal at the end of the competition.
Pausing a CTF will stop users from being able to submit answers. They will not be able to know if they got it correct or not, but challenges can still be viewed.