Cron to run first day of month to calculate date 3 months ago

Hi,

I would like to find out how can i calculate a date which is 3 months ago. I intend to run a cron job on the 1st of every month, and calculate the month 4 months earlier from the date. For example, if today's date is 1st May 2007, i would like to return 012007( January 2007).
i can get today's date by

'date +%Y%m%d`

is there a similar one liner or a few lines to achieve my result? would appreciate if anyone can shed some light. Thank you.

sorry, found many similar threads in the forum.

because i am using GNU date, i can get it by

date -d " x months ago"

depending how many months i need, just replace x with the require number.