Past date display ( today - N) in shell

Hi,

Any idea to get display of date - n ( n=1,2,3,4 etc) ?
For example , dtoudt will easily execute by dtoudt -3 and result is

>dtoudt -3
1234852529 Date 2009-2-17 time 14:35:29 day 47

How to get it display in 20090217 instead ?

Maybe you have other suggestion to display date -n

Thanks