Indeed, using the day as the fundamental unit may be a nice choice for humans on this planet as a personal system, it's equivalent to looking up and telling the time by the position of the sun in the sky, but it's not accurate nor regular due to celestial mechanics, so the second used by the metric system is much more universal and unlikely to change anytime soon.

Thanks to our computers that keep track of every seconds elapsed since Unix Epoch, I can use them when I want to convert from my personal system to any other system or vice versa:

  $ geodate 51.1789 -1.8262 $(date +%s --date "12:00 +0100") --format "%c:%b"
  45:33

hours:seconds => timestamp => centidays:dimidays