After watching your helpful webinar, I want to set up a filter for sending a 2nd welcome email to new signups to our list (the 1st one gets sent automatically by 123Contact working with NB). But I'd like to do a relative date of the last 3 weeks minus the date of that day. I can do: "became supporter is after or on 10/17/2017" AND "became supporter is NOT 11/7/2017" but this just means I'd have to do it again every 3 weeks, no? your documentation seems to imply I can do relative dates, but I'm not sure how. thanks!
Yes, you can use relative dates. Your filter criteria would be:
Became a supporter is in the last 3 weeks
Became a supporter is not in the last 1 days.
Here's how that looks in the control panel:
Complete and current information on how to use NationBuilder is available in the documentation section.