Here's what Delta says (for Sat, 05 Apr 2014 ):<quoted text>
can you say Asia is 12 hours ahead, and in the real world a flight in the air is a 2 day experience? Both directions.
Leave JFK:Delta 2942* 9:05am 05 Apr 2014
Arrive Beijing: Delta 0129 10:05pm 06 Apr 2014
And, coming back:
Leave Beijing: Delta 0188 4:50pm 05 Apr 2014
Arrive JFK: Delta 3321* 9:29pm 05 Apr 2014
Time zone changes always cancel each other out, if you return to the same place you left.