The question is when was the house your primary residence. The conservative answer is that the house was your residence until October 2014, which means you have to sell by October 2017 (minus 1 day) to use the exclusion.
A liberal risk-taking answer is that the house was your primary residence until Jan 4, 2015, which means you need to sell by Jan 3, 2018, to use the exclusion.
A realistic answer might be that the house was your primary residence until you "held it out for rental." That is to say, if you began advertising it as a rental and it was ready to rent as of December 1, 2014, then November 30 is the last date you could reasonably claim to be living there.
This issue is always what can you prove, if audited, because the burden on you is to prove your deductions and qualifications, the IRS does not have to prove anything. If you really moved out and were gone by October XX, 2014 then that's the date you were gone. If you were legitimately in a transition period for a few days or weeks you might get away with stretching the date.
