Using AM and PM.
AM and PM are also written A.M. and P.M., a.m. and p.m., and am and pm. Some put a space between the time and AM or PM.
• 8 AM
• 3:09 P.M.
• 11:20 p.m.
Others write times using no space before AM or PM.
For the top of the hour, some write 9:00 PM, whereas others drop the :00 and write 9 PM (or 9 p.m., 9pm, etc.).
Using numerals for the time of day has become widely accepted.
• The flight leaves at 6:22 a.m.
• Please arrive by 12:30 sharp.
However, some writers prefer to spell out the time, particularly when using o'clock.
• She takes the four thirty-five train.
• The baby wakes up at five o'clock in the #morning.