All you care about is the offset, regardless of whether time zones exist or not. Knowing the east coast is 3 hours ahead of us, I know calling at 8PM is probabl

All you care about is the offset, regardless of whether time zones exist or not. Knowing the east coast is 3 hours ahead of us, I know calling at 8PM is probably a bad idea. You don’t need that intermediate step of figuring out what number is associated with that on the east coast. You don’t care that Bob is in EST, you just need to know that he’s 3 hours ahead of you.