Simplify the following text for a Grade 8 native English-speaking person.
Original: Under the 24-hour clock system , the day begins at midnight , 00:00 , and the last minute of the day begins at 23:59 and ends at 24:00 , which is identical to 00:00 of the following day .
Simplified: In the 24-hour time notation , the day begins at midnight , 00:00 , and the last minute of the day begins at 23:59 .