You know the drill by now - a utility that rounds up every time-related function you can think of into the one title. The idea has been implemented on every other computing platform since the dawn of, well, time(!) and here it is under Windows 10 Mobile with 'Jack of Time' UWP...
Jack of Time provides a tool set of time related functions including a countdown timer with voice, stop watch, a time calculator, event timer, sunrise and sunset times, moon rise and set times, as well as a world time function with search--enter a place or thing (like "Statue of Liberty") and find the corresponding time zone and current time.
There's quite a bit to screenshot here:
Even on the opening view, there's a day and week number breakdown, which is surprisingly handy; (right) across the full set of half a dozen functions, here are the limits on the trial version. Nothing too limiting, though for a dollar, I'd recommend just jumping in to buy anyway.
Here I'm searching for the time in 'Seattle' and up it pops with its time zone and current time. Or you can just step though all world time zones; (right) a time 'calculator' lets you explore deltas...
For some, an all-important stat - a countdown to a future event - a holiday or concert, etc. "Only 104 days to my holiday!!" etc. (right) the stopwatch feature is very well done, with easy to hit controls and lap times overlaid.
You can have as many short term countdown timers as you like, each with custom titles and colours. And, obviously, they all 'run' at the same time and in the background if needed; (right) given your location (obscured here), both sunrise and moonrise times are calculated, along with other interesting stats. A nice little extra.