Why won't the date change?

Hi all.....
Can't find the answer to this one.
I was working on a drawing yesterday and saved it.
I went back later to access the drawing and panicked (could not find a
drawing with the correct date.)
I opened the drawing with the old date, and all my changes from yesterday
were there.
I saved it again...but it still maintains the old file date.
I have many drawings in this file and I have a couple of people working with
the set. It could get really
confusing if the dates are not correct...any ideas?
Windows 98
AutoCAD 2000
Thanks,
jojo