How to Manipulate Date based on number of days?
 

I have script where in i issue a command to get back 6 month earlier date.
below command works on all linux distribution.
Is there any solaris equivalent command to do the same?

You are using a GNU date extension. Check if GNU date isn't already installed, might be gdate, /usr/gnu/bin/date, /opt/sfw/bin/date, /usr/local/bin/date or something like this. Otherwise, you might install it from a freeware repository or compile it from source.