"This time last year I met my current wife." It always makes sense because "this time last year" implicitly refers to the time of year now. If you say this sentence now, you imply that you met your current wife in February, 2011. "That time last year I met my current wife." The question is "Which time was that time?"
They can both be correct. "At this time last year" means on or about February 22nd, 2011. "At that time" refers to a time that you mentioned earlier in the conversation.
So, which to use depends on the relationship between the time you're talking about and the time it is now, and on what time, or times, you mentioned before this sentence. We would need more context to say if one is right and the other is wrong.