[globular-toast]

You still have to know a bit about your buddy, though. You can probably assume he'll be awake at his midday, but what about 7:00? Is he an early riser? Or does he have other commitments at that time? In reality you'll just learn you can call around 16:00 your time. At that point it's just a number and doesn't matter what it is.

If things really were more complicated and you always needed to ask the question of "when can I call today", would it really be that difficult to incorporate schedules into contact records so your phone can tell you "available after 23 today".

[Tagbert]

Those schedules are just timezones in disguise

[globular-toast]

Sort of, but not really. I know what time is convenient to call my parents and they live in the same time zone as me. I don't work it out every time based on what the "normal" schedule is. And that's not to mention who actually calls people randomly over text now anyway?