Our time system is made up of 24 Hours and the sum of all hours does what we call day. This system for measuring hours starts at 0 and ends at 23.
On the other hand we find another system whose measurement is made from 12 hours to 12 hours.
Internationally, the preferred and most used system is the 24-hour system and thus it is homogenized in different continents.
24 hour service, it is called that because it is available all day, 24 hours without rest.