Travel conundrum

My mate who is also a well travelled man has decided that he is now 1 day older than his twin sister and she was born first. Due to the fact he has been across the international date line twice and has had 2 exta days of the day he crossed. Whereas she is still in the original timezone.

Is he right? or is this just a figment of his fevered imagination so that he has a younger sister than himself.

More to the point if he reverses the direction he travelled in…will he meet himself on the way back? :lou_surprised: