<P> The 12 - hour clock is a time convention in which the 24 hours of the day are divided into two periods : a.m. ( from the Latin , ante meridiem , meaning before midday ) and p.m. ( post meridiem , meaning past midday ) . Each period consists of 12 hours numbered : 12 ( acting as zero ) , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , and 11 . The 24 hour / day cycle starts at 12 midnight ( often indicated as 12 a.m. ) , runs through 12 noon ( often indicated as 12 p.m. ) , and continues to the midnight at the end of the day . The 12 - hour clock was developed over time from the mid-second millennium BC to the 16th century AD . </P>
<P> The 12 - hour clock is a time convention in which the 24 hours of the day are divided into two periods : a.m. ( from the Latin , ante meridiem , meaning before midday ) and p.m. ( post meridiem , meaning past midday ) . Each period consists of 12 hours numbered : 12 ( acting as zero ) , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , and 11 . The 24 hour / day cycle starts at 12 midnight ( often indicated as 12 a.m. ) , runs through 12 noon ( often indicated as 12 p.m. ) , and continues to the midnight at the end of the day . The 12 - hour clock was developed over time from the mid-second millennium BC to the 16th century AD . </P>
what is meaning of am and pm in time
what is meaning of am and pm in time
ante meridiem , meaning before midday post meridiem , meaning past midday
ante meridiem , meaning before midday post meridiem , meaning past midday