Ontime
Ontime is a free tool for planning meetings across timezones. Add the cities of the people you're meeting, pick a time, and see what time it is for everyone and whether it falls inside their working hours. Then add the meeting to your calendar or share a link.
You don't need an account to use Ontime. Signing in with Google is optional and only used to add a meeting you've planned to your own Google Calendar: Ontime creates that one event when you press "Add to Google Calendar", and never reads, changes or deletes anything else in your calendar.