Being before noon. "Ante meridiem" is commonly abbreviated a.m., A.M., or AM, and is used in time designations in the United States 12-hour clock system to indicate the morning hours. Noon itself is neither a.m. nor p.m., but the minute between 12:00 and 12:01 is p.m., so 12:00 noon is often denoted p.m. on digital clocks in the U. S.