if you have GNU date and i understood you correctly
$ date +%Y:%m:%d -d "yesterday"2009:11:09
or
$ date +%Y:%m:%d -d "1 day ago"2009:11:09
If you have BSD (OSX) date you can do it like this:
date
date -j -v-1dWed Dec 14 15:34:14 CET 2011
Or if you want to do date calculations on an arbitrary date:
date -j -v-1d -f "%Y-%m-%d" "2011-09-01" "+%Y-%m-%d"2011-08-31
date --date='-1 day'