The One With Ross' New Girlfriend - S2-E1
Corrected entry: In the first episode of the second series, Ross mentions to the group that, after returning from Beijing, it was six o'clock the next evening to Julie and himself. This is impossible; when it is six p.m. in Beijing it is five a.m. in New York, so it would be that time and it seems strange that they would all be gathered at Monica's apartment and Rachel would have just concluded a date (in the last episode of the first season) at such a time. For it to make any kind of sense, Ross would have to have returned from, say, New Zealand, and it would be one a.m. EST, which would be slightly more believable.
Correction: Given the way Ross makes this remark, it is not meant to be taken literally. He has just been travelling for a loooong time and is trying to highlight the time difference. This is exactly the kind or remark most of us would make after passing through multiple time zones.