How to get files modified after certain # of days

[daledude]

I'm a bit confused about the date parsing. I'm trying to query for files that are older than 90 days but it doesn't return anything. Can you please give an example of this?

fselect "path from /usr/local/old,/usr/local/old2,/usr/local/old3 where modified gte '90 days' order by modified desc"