As of now, expect 2 days for the time period to reset, but it could be sooner.
Flag bans are automatic based on recent flag history, both being put in place automatically after a certain threshold of declined flags, and being lifted once the declined flags leave the time threshold for being counted.
While moderators are usually the ones who handle the flags and as such are the cause of a flag being marked helpful or declined, moderators take action on the flag itself and not the user who raised the flag.
Each flag is handled independently (except in rare cases such as with custom flags providing background information that should be handled) and flag bans are not ‘given out’ to users manually by a moderator.
Therefore a moderator cannot remove a flag ban, no matter how nicely someone asks on meta!
As the flag ban is based on recent flags, as time goes past previously declined flags fall out of scope of the formula used to determine whether you should be banned from flagging. Since this formula is based on recent flags and can change over time, this date is not presented to you.