a change in 'last modified time' does not equal a change in file
Moreover, the scripts are not actually being modified, or if they are, they shouldn't be. That is: if the files' last-modified time changes, that would mean that mIRC erroneously modifies them as a result of the time shift. If the files' last-modified time does not change, then mIRC is drawing the wrong conclusion based on the time shift. Either way, it is a bug in mIRC.
It's an ancient one, too, but a fix would still be much appreciated. Hashing the files should not be a required part of any solution, either (although doing so may be beneficial in some other use cases).
(15 scripts loaded usually means you get 15 prompts whenever this is happening, sorry but no thanks)
Just FWIW: it is possible to hold the Esc key to get rid of them all in one go (after all, the files haven't actually changed).