Let's say my character casts a spell as a swift action during his turn and this spell gives a bonus to all characters in a 30 ft. radius around him "until his next turn".
Is it the start or the end of my next turn? Or does it depend on when in my turn I cast it?
In other words, do I get the benetits twice or potentially not even once if I cast it at the end of my turn?
(This question comes from a player using a martial maneuver from Path of War at the end of their own turn to buff their companions, but I guess it's valid for all spells and similar effects too, so I have generalized it.)