You want to use the hidden fields as a way to track what the original value
was for each date. So that, on your action page, you can compare what the user
entered to the original value (the corresponding hidden field) to see what's
changed and make the necessary update(s).
So the VALUE attribute for your hidden fields should be set to the original
date value (not TRUE)...
(On a side note, the way you're incrementing the DTE variable looks funky to
me. If I'm not mistaken, I think that'll convert the NOW() date object to a
millisecond representation. Not sure if that's still the behavior, though.
Might want to use the DateAdd() function instead.)