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how do you correctly spell out time of day -- is it 7 p.m., 7:00 pm, 7pm, 7 P.M., ????
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7 p.m., 7 pm, 7 PM look okay to me.

"Both a.m. and p.m. sometimes appear in capital letters, especially in printed matter."
RHUD

In British English the periods are often left out.

CB
Comments  
7:38 p.m.
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7 p.m.
Whenever pm or am is involved, use the numeral: 7:00 pm. Whenever "o'clock" is involved, spell out the number: twelve o'clock at night. If time is written in an essay, try to use words if possible: twelve-thirty in the evening.
seven o'clock in the evening
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 Cool Breeze's reply was promoted to an answer.