1. Keep it short & sweet: "4:00 pm"

2. Get a 'lil fancy: "at half-past four o'clock in the afternoon"

- Make sure you are including a hyphen when you say "half-past" or "quarter-after" AND the ' in o'clock!

IMPORTANT:

Sunlight to 12:00 pm: Morning

12:00 pm to 5:00 pm: Afternoon

5:30 PM to 9:00 pm: Evening

FOR EXAMPLE:

at five o'clock in the afternoon

or 

at half-past six o'clock in the evening