How Does Daylight Saving Time Work?
https://www.timeanddate.com/time/dst/transition.html - explained very well.
day minutes hours and seconds breakdown
It was useful for sailors to be able to divide the day into shifts, so our day is the most divisible number of hours long.
1 x 2 x 3 x 4
That way you could have half days, quarter days, or third of days.
An hour is divided into 60 minutes: 3 x 4 x 5
The word "second" means a "second division by 3 x 4 x 5"