Does update-date filtering work on the Activity API?

[Gordon Robinson]

I'm trying to use the activity stream API on my version of Jira.  It works when I try and filter on username, but when I try and filter on update-date, e.g. "update-date+IS+BEFORE+1733097600000" then it doesn't work.  Any tips on what I could be doing wrong?  Is there good documentation on this API anywhere?

I'm using version 9.4.23.