The 114th Congress adjourned sine die on January 3, 2017. The 115th Congress convened on January 3, 2017 one hour later. Obama was still President until January 20.
The 115th Congress is targeted to adjourn on December 14, 2018. Of course, this may change.
-PJ
I guess I'm perplexed why people think it will be different this year. The senate led by republicans have not officially adjourned because the republicans have stated on the record they do not want Trump to make recess appointments.
So, forget the House having to give permission, if the Senate has not officially recessed, not even one time to prevent Trump from making recess appointments, why would they now recess before the next Congress?