Wierd thing I've noticed recently. Just right clicking a folder (which opens the context menu) then closing it again will change its date modified to the current date and time.
I created two (empty) folders.. waited a bit, then right clicked folder "2"... and the date changed to the current time:
Wondering if it is somekind of (buggy) explorer extension that might be causing this, or if others are also seeing it.
Autoruns lists these: