The question you ask now is "what time is it in X place?" if you want to know if its reasonable to call someone.
But that is insufficient knowledge. You also need to know their work schedule, when they prefer to sleep, if they are busy that day. You call people regularly who are preoccupied or who just aren't in the mood.
I have two cousins who share a time zone apart from mine, but one works the night shift. So one sleeps 10-18 and works 22-06 their time and the other sleeps 23-07 and works 09-17. If you call one in their in between hours one is just waking up while the other is tired, in the same time zone.
You cannot even just assume "people everywhere wake up at 7 and go to bed at 11 within their timezones" because timezones are not consistent between countries, within countries, or across continents. Different cultures have different daily routines and schedules.
This is why people have just gradually, especially in newer generations, gravitated towards asynchronous communication as a default.
On the flipside, if you wanted to ask the question "we are on the same universal time, is it safe to call X?" you are asking a better question anyway since you need to know the regular available schedules of people where that person lives, just not on your presumed "normal" timetable.
Travel alarm clocks are a great topic, because they already require manual intervention for all the aforementioned time zone inconsistencies. To build a working "automatic" travel clock you need a full computer with GPS to do precise location to map you to the TZ database and then to also look up sunrise and sunset because those aren't consistent even with timezones.
An "everywhere is UTC" clock requires just as much hardware, but only one question - when is sunrise here? Because you just set your wakeup time near that if you are diurnal. Which not even everyone is. Especially in the hacking space where there are plenty of night owls.