If you're calling a specific person, you very likely know where they are. People don't move around that much. If he's not in his usual place, he's probably told you where he is if he's expecting a call from you. And even then, if it doesn't want to reveal or burden you with knowing where he is, we already have a universal time stanard he could use for this ("call me at 13:30 UTC").

Decoupling time-of-day for daily life from the position of the sun in the sky is the biggest over-reaction for the smallest barely-a-problem ever.