I need to get all the question activity after some particular time. I am using the timeline API, like so:

/questions/20032212/timeline?fromdate=1384705610&site=stackoverflow.com

But it returns no comments! Even though running the query with a much earlier date, EG:

/questions/20032212/timeline?fromdate=1384700712&site=stackoverflow.com

shows a comment with a creation_date of 1384705710 -- which obviously is greater than the 1384705610 in my original request.

Can somebody shed some light on this behavior?
What is the best way to get question activity that occurs after a certain time?