If the position of the sun is truly important to your use case then knowing a location is "UTC+9" as far as sunshine hours go is still able to tell you that without requiring you encode that information into the time value itself.
This is already answered in the post you are replying to, so I assume this is you demanding an external source:
I hear you on waking time. For that I've build the "Meeting Time" feature that makes sure to find the best time for a meeting for different locations where it's a good time to meet for everyone. For example, the best time to have a meeting between San Francisco, New York, London, and Berlin is between P-R baring in mind that the clock makes sure that the meeting is between 8am and 19 (7pm) for everyone. And this is all configurable :) You can also share the link of the meeting time as this one https://thehtime.com/intersect?locations=USA+-+San+Francisco...
Happy to hear your thoughts on this feature.
You're right, this clock doesn't remove the local times and replace them with UTC; instead this clock overlays the local times with a replacement "A-X time", which is a single timezone applied to everywhere. Not UTC, but a new, non-standardized "DIY" UTC. That's the whole thing it does: throw away the location-specific "daylight-hours" quantifier (the "hour" part of the time) and replace it with a "single timezone" version (where it's "F:30" everywhere on earth at the same time), but instead of the globally-recognized standard of UTC, it's a brand-new standard that arbitrarily uses letters rather than numbers (with an "origin point" that's unclear -- where in the world is A:00 equal to 00:00? I couldn't find it, so I couldn't easily figure out my timezone's offset so that I could reason about daylight hours).
I've seen clocks that do this already, but with UTC instead of "A-X time": they have two "dials", one for local time and one for UTC. That's all this is, just with letters instead of numeric hours (an arbitrary substitution) and a newly-made-up "base" timezone instead of UTC.
There's no functional difference between consulting a clock like this so that you can say "F:30" to all of your teammates and it'll be the same time everywhere, and consulting a UTC clock so that you can say "10:30 UTC" to all of your teammates and it'll be the same time everywhere, except that most people have memorized their local UTC offset and can go "oh, okay, 10:30 - 5 hours = 5:30", where with F:30 they have to go consult your website instead.
Having a configurable "meeting time" feature is neat, but like...that's an extra tool you had to build on top of your clock system, not an intrinsic feature of your clock system itself. I need a complex translator tool to tell me what A-X hours are reasonable for meeting with people because I can't just simply apply offsets in my head and get intuitive results (especially because the "base" offsets are unclear).
I think a lot of folks overestimate how painful it is to do modulo addition/subtraction, compared to how painful it is to learn an entirely new system of timekeeping-and-translation.
Would love to hear your thoughts on the rotating UTC layer vs an extra UTC layer + hand.
Yes, with timezones and UTC-offsets I have to keep in mind that 8:00 in my timezone might be 3:00 in someone else's timezone, but once I do the simple math of adding the offsets and doing any necessary modulos, I now know that the meeting time I've chosen almost certainly isn't a reasonable meeting time for that person.
I know from experience that for the overwhelming majority of people in the world, 3:00 is still probably sleeping time, regardless of what timezone that 3:00 is in. 3:00 in UTC is sleeping time in London, 3:00 in UTC-5 is sleeping time in Atlanta, 3:00 in UTC+9 is sleeping time in Tokyo -- in any case, 3:00 is sleeping time.
Attempts to have "one world timezone", even leaving out the existence of fractional-hour timezone offsets, will always throw away that semantic detail about human schedules.
For example, let's say you just enforce that everyone uses UTC. Congratulations, you no longer have to do offset math.
Except that you have no idea if 10:00 is a reasonable meeting time for anyone within a few timezones of you (which remember, no longer exist, so you can't really use them as references). You no longer have to memorize each participant's offsets, but now you have to memorize the daylight hours for each participant instead, and that's arguably harder (X's daylight hours are 8:00->16:00, but Y's daylight hours are 14:00->2:00, but then Z's daylight hours are 12:30->20:30).
Yes, there are companies with overseas contracts who dedicate some staff to working the same hours as their overseas counterparts. Do we really want that to become the global norm, though? Because if not, then "daylight hours" remains an important concept, and it's already baked semantically into the system of timezones we have today, more simply than the alternative.
So if we toss out the piece of information that conveys the detail about "daylight hours" (which is what this clock does with its letters-instead-of-hours), then we're losing that information, and making it much easier to trample all over somebody's reasonable working schedule.