This has been bugging me for a while and I've finally got round to trying to sort it out, so perhaps somebody could explain the usage to me. As far as I am aware hace can be used to mean 'for' or 'ago', but how do you know the difference?

e.g.

I lived in Buenos Aires for 6 months

Hace 6 meses que vivía en Buenos Aires (?)

or

6 months ago I lived in Buenos Aires

Hace 6 meses que vivía en Buenos Aires (?)

So is one (or both) of the above incorrect? How do you say the above examples properly?

Thanks for your help!