Support » How-To and Troubleshooting » AM and Pm in post?
11 years, 1 month ago
How do I set the timestamp to PM from AM?
http://codex.wordpress.org/Formatting_Date_and_Time has the information for setting all the times.
But changing from PM to AM means changing the time in your Admin Panel > Options > General panel, set the time for you according to your UTC time.