Intensive care unit (ICU) means that the patient's condition is critical and may change at any time, which requires 24-hour continuous monitoring by nurses, that is, one nurse sees one patient 24 hours a day.
The 24-hour clock system refers to the design method and composition scheme of clocks and watches, that is, it is a kind of pointer indication that changes the traditional clocks from two turns to one day, with 24 o'clock as 0 o'clock in the morning and 12 as noon 12.