I think you need to do it in two steps.
Search for (?<=\d)- (that's a hypen preceded by any digit)
Change to <space>$0 (the <space> is a standiin her for the ype of space you are using, so use the real thing in the dialog)
then Search for -(?=\d) (that's a hyphen followed by any digit)
Chage to $0<space>
It's tempting to add spaces to *all* numbers separated by a dash. If you are sure all times have a minutes part, then it's safer to use this:
(?<=:\d\d) ?- ?(?=\d)
.. replace with space dash space.
It searches for "colon, any digit, any digit" (which is *found* but not *included*), followed by "one optional space, a dash, one optional space", and must be followed by "any digit" (again, not including this last one). Since the numbers before and after are *found* but not *included* -- that's due to the (?xxx) syntax -- all that needs replacing is the dash itself. By making the space before and after the dash optional (using a single "?" immediately after each), it doesn't matter if there *is* a space or not, all combinations will be found and replaced.
Thank you. I'm brain dead today.
Thanks for the help, everyone!