I've been a big fan of worldtimebuddy[1] for a long time. I book a lot of meetings across timezones and it's makes it very easy to see when a good time for a meeting would be between sydney tokyo and miami as an example
Out of curiosity, would you prefer to see all the options laid out so you can quickly scan which ones would be optimal? Or would you prefer to click a button and then it just schedules the meeting for you?