AM and PM: There are two ways of representing time – the first is through the 12-hour clock, and the second is through the 24-hour clock. According to the 12-hour system, 24 hours is divided into 2 periods, each lasting for 12 hours. The initial 12-hour period, which lasts from midnight to noon, is designated with AM, while the next 12-hour period, which lasts from noon to midnight, is set with PM.

“AM” and “PM” are both abbreviations of Latin terms and refer to a specific time of the day. AM – ante meridiem, means “before noon”, referring to the morning (before the meridian line has crossed the Sun). PM – post meridiem, means “afternoon”, so it refers to any time after mid-day to till night (after the meridian line has crossed the Sun). We can say the time from midnight to noon (or from \(00:00\) to \(12:00\)) is AM. The time from noon to midnight (or from \(12:00\) to \(24:00\)) is PM. In this article, let’s discuss this in detail.

AM and PM Meaning With Example

Time is divided into hours, minutes, and seconds. Each day is \(24\) hours, each hour is \(60\) minutes, and each minute is \(60\) seconds.

The \(12\)-hour clock method defines all \(24\) hours of the day using numbers \(1\) to \(12,\) followed by am or pm.\(6\) AM is early in the morning and \(6\) PM is late in the afternoon; \(2\) AM is two hours after midnight, and \(10\) PM is two hours before midnight. Ante meridiem is generally referred to as AM, am, a.m., or A.M, whereas PM, pm, p.m., or P.M. are typically abbreviated as post meridiem.

Representation of AM and PM on a \(24\) Hours Clock:

Let us include everything about AM and PM in one picture,

12 Vs 24 Hours

There is always an ambiguity of \(12\)-hour clock convention, and many establishments require that this time representation should be discarded altogether. It could be used in conversations and informal communication only.

However, the legal documents, schedules, and other interactions that require high precision time identification should follow the \(24\)-hour format to avoid confusion with the denomination of noon and midnight. For instance, the confusion of whether \(12\) o’clock is \(12:00\) or \(00:00\) is the most common issue for the AM/PM format.

AM & PM Difference: Midnight Confusion

Another confusion is the lack of a date designator in the \(12\)-hour system, making it impossible to logically identify a suitable moment in time when only a date and \(12:00\) am (midnight) is provided. Just imagine being asked to pick up a friend at the railway station at \(12:00\) am on April \(21.\) Would you go there at midnight between April \(20\) and April \(21\)? Or \(24\) hours later?

One way to overcome this problem is to sacrifice accuracy for clarity. Your friend could ask you to be at the railway station at \(21:01\) am on April \(21\) or, if the following midnight is meant, at \(11:59\) pm on April \(21.\) Alternatively, the \(24\)-hour format could be used. Here, \(0:00\) refers to midnight at the beginning of the day, while \(24:00\) is midnight at the end of the day.

Convert AM and PM clock to 24-hour Clock

1. To convert AM and PM clock into \(24\)-hours clock subtract \(12\) hours from the first hour of the day (midnight to \(12:59\) AM).
Example: Convert \(12:40\) am into \(24\)-hour clock.
Now, \(12:40\,{\text{AM}} = 12:40 – 12:00 = 00:40\)
Hence, \(12:40\) AM is \(00:40\) in the \(24\)-hours clock.
Note: The hours and minutes remain the same from \(1:00\) AM to \(11:59\) AM

2. Add \(12\) hours for the time ranges from \(1:00\) PM to \(11:59\) PM.
Example: Convert \(3:20\) PM to \(24\)-hour clock.
Now, \(3:20\,{\text{PM}} = 3:20 + 12:00 = 15:20\)
Hence, \(3:20\,{\text{PM}}\) is \(15:20\,{\text{PM}}\) in the \(24\)-hours clock.

Convert 24-hours Clock to AM and PM Clock

1. To convert \(24\)-hours clock into AM and PM clock, attach \(12\) hours from the first hour of the day (\(00:00\) midnight to \(00:59\)) and AM to time.
Example: Convert \(1:30\) into AM and PM clock.
Here simply add AM to the time, from \(1:00\) to \(11:59.\)
Thus, \(1:30 = 1:30\,{\text{AM}}\)
Hence, \(1:30\) AM is the AM and PM clock format.

2. Subtract \(12\) hours and, in the end, add PM to the time for intervals between \(13:00\) and \(23:59.\)
Example: Convert \(16:50\) into AM and PM clock.
Thus, \(16:50 – 12:00 = 4:50\) PM
Hence, \(4:50\) PM is the AM and PM clock format.

AM and PM Rules

1. Lowercase a.m. and p.m. and always use periods.
2. Lowercase noon and midnight.
3. Do not use \(12\) noon or \(12\) midnight (unnecessary). Use noon or midnight only.
4. Do not use \(12\) p.m. or \(12\) a.m. Use noon or midnight.
5. Do not use \(8\) a.m. in the morning (unnecessary) Use \(8\) a.m.
6. Do not use o’clock with a.m. or p.m.

AM and PM Notes

For the people who just experienced the \(12\)-hour convention, it might be not easy to memorize or know to what part of the day AM and PM refer. However, a simple solution does not even require knowing the actual translation of the abbreviations (ante/post meridiem).

AM starts with the first letter of the alphabet, \(‘A ‘\). Considering that AM corresponds to the start of the day, knowing that \(‘A ‘\) signifies the beginning of the alphabet could be a perfect point of reference for memorizing. Meanwhile, the fact that AM is alphabetically closer than PM should be the designation that it is before midday.

Solved Examples – AM and PM

Q.1. Convert \(18:00\) to \(12\) hour clock time by using AM or PM units.
Ans: To convert \(18:00\) to \(12\) hour clock time, we subtract \(12\) hours and at the end add PM.
Thus, \(18:00 – 12:00 = 6:00\)
Hence, on converting \(18:00\) to \(12\) hour clock we get, \(6\) PM.

Q.2. Convert \(9:49\) am to \(24\)-hour format.
Ans: Here, we need to convert \(9:49\) am to \(24\)-hour format.
To convert the time from \(1\) am to noon, do nothing, simply remove the unit i.e. am.
Thus, \(9:49\) am \(=9:49\)
Hence, \(9:49\) am in \(24\)-hour format is \(9:49\)

Q.3. Convert \(12:50\) am to \(24\)-hour format.
Ans: Here, we need to convert \(12:50\) am to \(24\)-hour format.
The time from midnight to \(12:59\) am, subtract \(12\) hours to convert the time to \(24\)-hour format.
Thus, \(12:50\) am \( – 12:00 = 0:50\)
Hence, \(12:50\) am in \(24\)-hour format is \(0:50.\)

Q.4. Convert \(20:00\) to \(12\) hour clock time by using AM or PM units.
Ans: To convert \(20:00\) to \(12\) hour clock time, we subtract \(12\) hours and at the end add PM.
Thus, \(20:00 – 12:00 = 8:00\)
Hence, on converting \(20:00\) to \(12\) hour clock we get, \(8\) PM.

Q.5. Convert \(10:30\) to the \(12\)-hour system.
Ans: Here, we need to convert \(10:30\) am to \(12\)-hour format.
To convert the time from \(1:00\) to \(11:59,\) just add am after the time.
Thus, \(10:30 = 10:30\) am
Hence, \(10:30\) in \(12\)-hour format is \(10:30\) am.

Frequently Asked Questions (FAQ) – AM and PM

Q.1. How do I know it’s AM or PM?
Ans: The \(12\)-hour clock divides the \(24\) hours of a day into two periods, \(12\) hours each. The first \(12\) hour period is designated as AM. It runs from midnight to noon. The second \(12\) hour period, is marked PM. It runs \(12\) hours from noon to midnight.

Q.2. Is \(12\) in the morning AM or PM?
Ans: \(12:00\) am (midnight) occurs instantaneously after the end of the previous day and is therefore also the start of a new calendar day for a particular time zone.
\(12:00\) pm (noon) is the end of the morning on the same calendar day. Using the prime meridian again (GMT) the Sun is now directly over Greenwich. So, \(12\) in the morning is AM.

Q.3. Is \(6\) pm Morning or night?
Ans: AM and PM are used in \(12\)-hour clock system. Accordingly, \(6\) am is early in the morning and \(6\) pm is late in the afternoon. So, \(6\) pm is night.

Q.4. Is \(11\) AM in the morning?
Ans: \(11\) AM is late morning. \(12\) noon is when it changes from AM to PM. Midnight is when it changes from PM to AM. So, \(11\) AM would be late morning.

Q.5. Is AM Night or Day?
Ans: AM means “before noon”, so it refers to the morning. PM means “afternoon”. So, AM is the day.

In this article, we covered the definition of AM and PM, the full form of AM and PM, the meaning of AM and PM, Notes, some rules to write AM and PM, AM vs PM, how to convert \(12\)-hours clock (AM-PM) to \(24\)-hours clock, how to convert \(24\)-hours clock into \(12\)-hours (AM-PM) clock, and some solved examples. Check out Embibe to clear all the doubts and confusion about AM and PM.