how to grep this date format

2008-01-10
2008-01-05
2008-01-02

i wrote the format as

date +"%Y-%m-%d"

but this format is showing me the current date i,e 2008-01-11....i dnt want current date i want the previous date.

so plz any1 help me in giving me the date format for grepping other dates other than todays date.................