how to deluge for negative dates

I'm trying to create a report that will filter to identify records with no activity over the past 5 weeks and feel like there is probably a deluge script that I'm just not finding.

Any suggestions on how I tweak the following to also exclude records that have activity in past 5 weeks?

show all rows from Accounts [(Activities.Activity_Date >= (zoho.currentdate - '5W:0D:0H:0M:0S')]