I have a new home and would like to know at what date my residence would qualify for an exclusion of $250,000 in capital gain?

I am planning to sell my primary residence. 


I would like to know at what date my primary residence would qualify for an exclusion of $250,000 in capital gain. 


Because this is a new construction situation, I am unsure of when the "ownership" and "residence" requirements began. 


Here is the situation: 


I purchased the building lot in September 2014. 


I moved into the home on January 1, 2016 and have lived in it full-time since that date. 


My construction loan matured and converted to a permanent loan on July 1, 2016. 


I did not have an official certificate of occupancy until May 5, 2016. There were a few lingering issues that prevented full occupancy until that time. However, we were living in the home full-time. 


When can I sell and avoid the $250,000 in capital gains? Since I was living in the home since January 1, 2016 would the 2 year "residence" and "ownership" clock have started then? How would this standup if I were audited? 


Thank you in advance