Welcome @d-ring
I know you can compare two dates that are in the same format (eg ISO8601 ) like this:
if [date1] <= [date2] {
}
But as you say, that would require you to create another date field for 30 days ago.. In this post => Adding 1 day to the date
something similar is done with a ruby filter, please check that out and see if you can make it work.
Grtz
Willem