This might be useful: https://www.timeanddate.com/worldclock/meeting.html
I once scheduled an interview with someone on the West coast (I'm on the east coast). I emailed him in the morning "How about 4 o'clock?" That afternoon around 2 I checked my email again and got his response "great, you can call me at 1." I freaked out for a second thinking I had missed the appointment, only to realize he meant 1 pm his time == 4 pm my time.
Aviators/Military solve that by using Zulu time I believe (ie UTC).
UTC, yes, but that doesn't resolve the problem of establishing office hours. At least when you do explain those you don't need to constantly convert.
"Here we work from 17h to 23h" is a lot easier to understand "Here we work from 9 to 5, but we're in summer time, so that's actually an hour off of the usual thing but...oh, wait, you're on summer time now too, so I guess it's the usual plus six hours, no wait, minus six..."
One planet, one time-zone, and everyone can keep their local customs for waking/sleeping, working, and whatever else.
I've resolved that by pointing to my Calendly page and have people pick the time themselves. Of course that doesn't work well if there are multiple parties, but even then it helps to point them at it to find out when I'm available (giving shared access to the actual underlying calendary would work too, of course, but my Calendly page shows specifically when I have decided I'm free for meetings)
http://www.worldtimebuddy.com shows a very visual representation that could be helpful to you.
"Great, sounds like we have a plan. When should we touch base again?"
"Let's aim for Monday. How's your afternoon?"
"Monday is no good, but Tuesday morning is free."
"Um, mornings are no good for me, I'm on the west coast. I could do anything after 10am your time."
"OK, 1pm works."
"1pm your time, great."
"Oh, no, I meant 10am your time, 1pm eastern."
"Oh, right, ok. Great, I'll send a meeting invite."
Time zones make this SO INSUFFERABLE. I'm in the Bay Area now, and everybody still reverts to ET just to speak about the same thing. I actually have a biweekly call with people in DC, New York, Chicago, and SF, and it's hell to try to move by an hour. Everybody ends up speaking relative language, about "push it back an hour" or "same time tomorrow?". There's still going to be problems with the east coast thinking 10am is a good time to meet, or people who are on the hook to spend money dragging their feet for no reason, but I would love to get everybody working on the same system.
(As a side note, meeting invites that work over email are god's gift companies. Getting on the conference call at the wrong time is remarkably rare, and nobody ever blames time zones, because software takes care of the problem once you've picked the initial time.)