set field (TheField;get (current date) - 30)
not sure if 'current date' is correct, could be 'system date' (don't have an english system here)
Perfect Markus. It was current date. Thank you.
It's probably not a big deal, especially for this particular need, but we've gotten in the habit of using getasdate ( get ( hosttimestamp ) ).
This ensures that dates (and times) are consistent across users in a multi-user environment. In some cases, it's also important to ensure that the user can't change their local date and "time travel" to enter dates they wouldn't normally be allowed to enter.
Just a (loosely) related thought.