Free Membership - how long?

Recently I get this gift. Thanks chess.com. But for how long?

Why did I get it? Randomly?

Usually shows up around the one year point.  A pity we can't swap it for three times the duration in Gold membership.

sftac

CapilanoBridger, it was not random.  You probably hit a certain number of points (for posting, usually) and this site awards that once or twice.  That's how I created the EZS without paying for it.

I believe it used to be one month but perhaps it was one year. 
The time frame seems to be deliberatelty vague.

Oh, right.  On your free Diamond trial you could (as others no doubt have done judging by the number of groups here), start up a gadzillion "groups".  Of course once your trial is over, you'd no longer be super duper admin, but perhaps someone else would step in.

sftac

No I'm still the only S.A. of the EZS.

I believe I had Diamond status for a week because I referred someone (who explicitly mentioned that I referred her to this site).   I'm aware I'm contradicting myself ten minutes later, but it was awhile ago.

He has about 100. I have 5000 and still didn't get it.