Looking for exact closed date for closed items

[Mechanicoo]

Hi, 

I am working on a personal reporting script and looking for a way to get exact closed date-stamp for closed tasks. Currently I see that updated_at is available but does it always represent correct closed date-stamp even if task is moved/edited after it has been closed.

Similarly, how can I get same details for invalidated tasks?

Regards,

Umar.