Why decimal?
A day has 86,400 standard seconds, split as 24 × 60 × 60, which then go back to base ten for fractions of a second. Decimal time splits the same day into 10 hours of 100 minutes of 100 seconds: 100,000 seconds in all, each one 0.864 standard seconds long.
The nice part: decimal time is the fraction of the day. 4:37:52 means the day is 43.752% done. Noon is 5:00:00. Six in the evening is 7:50:00.
Tap any clock to make it the big one. Type a time at the top to convert it; every clock jumps to that moment.