I'll be completely honest, it could be less time for all I know
I play on these servers mainly, so i just took my tf2 hours and subtracted a certain amount to make a guess. I didn't know how to find out specifically how much I've been on these servers, so I just went for that.
Concerning the issue of seeing me on servers, I used to change my name a LOT (I only just stopped a few days ago,) so that could be it. One name i've used frequently in the past is Pugplays42, but as of the moment it's currently "Sunny the Lord of Cringe".