The instinct is to solve time zones with more tools — a shared calendar, a scheduling link, a Slack status. Those help, but they don't solve the actual problem, which is that someone still has to be awake when a decision needs making.
Coverage, not overlap
Most founders default to wanting full overlap with their assistant's hours. In practice, you don't need someone awake exactly when you are — you need someone awake when the actual work happens, which is often earlier or later than your own schedule.
A well-matched assistant working four hours before your day starts means your inbox is already triaged by the time you sit down. That's more valuable than four hours of live overlap spent on things that didn't need you anyway.
Write down what needs you, specifically
Anything that requires your judgment, your voice, or a decision only you can make should be flagged and routed to you directly — everything else shouldn't wait on your time zone at all.