Heather - It really isn't clear what you are trying to accomplish.
Perhaps some examples with actual dates and results would help us
understand.

Without that, I'll try to take a crack at some concepts.

First off, the date "format" for cells Q7 and M7 is just a format. The
underlying value is a serial number. For instance, today's date
(08/12/2005) in serial format is 38576. 8/13/2005 is 38577 so each
digit is equal to one day. Subtracting one date from another gives the
number of days between the two but adding two dates doesn't make much
sense.

If you add, 8/12/2005 and 8/1/2005 the result will be 3/15/2111 since
what you are really adding are 38,565+38,576 which equals 77,141 which
when formated as a date is 3/15/2111. Add 30 days to that and you'll
get 4/14/2111. I can't imagine why you'd want to do that.

On the other hand, if you want to add 30 days to the elapsed time
between two dates that might make more sense. Using the serial numbers
for 8/12 and 8/1 for purposes of illustration, 38576 - 38565 = 11 or
the elapsed days. Since these are elapsed days NOT a date, you would
format them as a number not a date. Add 30 days to that and you'll get
a total of 41 days.

I know this doesn't answer your question but it should give you some
clues on working with dates. Give some more specifics in your example
and I'm sure we can help.

- John