Headcount on a date filter

Morning all!

I'm really stuck on this one so any help would be amazing!

I'm looking at a list of employees with various start and end dates over a rolling 12 months. 

The employee data has anyone who started prior to the 12 months and anyone who ended from 12 months ago up until today. 

What I'm trying to do is filter to any date in the past 12 months and see the head count at that date. 

Is this possible?