help needed in date format

Shell Programming and Scripting
1

i need to grep date in the format year-month-day,,,,,,,
actually i need to grep those dates other than current date..........

can anyone help me in this...........i need a format of date which would grep previous date except current date

2

Either
grep -v `date +'%y-%m-%d'` /yourpath/yourfile
OR
grep -v `date +%Y-%m-%d'` /yourpath/yourfile

Only difference is the year format - first one does 08, second one does 2008.