Hello angelinechuah. I'm not quite sure what you mean. Have you heard a particular phrase relating to time, and you want to know how to use it?
The most common ways of saying the time would be things such as:
"It is half past four in the afternoon." (4:30PM or 16:30PM)
"It is one o' clock in the morning." (1:00AM or 01:00AM)
"It's quarter to eight at night." (7:45PM or 19:45PM)
The numbers to the right of the words are from different types of clock. The first time I gave in brackets in each example is from a 12 hour clock. AM is before mid-day (12:00PM), PM is after mid-day. 7:00AM would be the 7th hour of the day, where as 7:00PM would be the 19th hour of the day.
The second time I gave in each example is from a 24 hour clock. So 14:00PM would represent the 14th hour of the day, which in a 12 hour clock would be 2:00PM.
I hope I've answered what you asked, or at least understood what I've said.