When most people say 12pm, typically they're talking about the middle of the day: 12 noon. When they say 12am, they normally mean 12 midnight.
Both 12am and 12pm are precise moments of time. 12am is the exact moment the 12th hour of the morning finishes (am), and similarly for pm. Therefor 12am is midday and pm would start straight after. The confusion has started since the invention of the digital clock.
So technically, 12AM and 12:30PM is just afternoon, which technically is 12PM. So to avoid confusion, many people do not use 12AM or 12PM, and prefer to use midnight for 12AM and noon for 12PM. So afternoon begins at noon, and runs until evening.
In 24-hour (military) time, 12:00am is equal to 0000 and is read as “0 hundred hours”. 1:00am, or 0100, is pronounced as “zero 1 hundred hours”. The rest of the hours between 12:00 AM and noon on the 12-hour clock are equal to the hours between 0000hrs and 1200hrs.
> Simply, lunchtime is 12 noon.
It is common in transport timetables to use 23:59 Sunday or 00:01 Monday (in this example), or 11:59 p.m. or 12:01 a.m., to further reduce confusion. There are no standards established for the meaning of 12 a.m. and 12 p.m. It is often said that 12 a.m. Monday is midnight on Monday morning and 12 p.m. is mid-day.
The 12-hour clock runs from 1am to noon and then from 1pm to midnight. The 24-hour clock runs from 00:00 (midnight) to 23:59.
Noon is 12:00PM. Some think it is 12:00AM, but it isn't, that's midnight. PM means post meridiem (after noon) and AM means before noon, so there is confusion as to what noon is, but there is no confusion that the hour after noon is PM, so 12:01-12:59 is PM, post meridiem, after the sun has passed the meridian.
As the dividing point between one day and another, midnight defies easy classification as either part of the preceding day or of the following day. Though there is no global unanimity on the issue, most often midnight is considered the start of a new day and is associated with the hour 00:00.
Midnight is 12:00 pm. It is also 00:00 am. This is because it represents both the beginning and the ending of a set of numbers that runs from 00:00 to 12:00. It then changes to 00:00 instantaneously and begins again.
12.30 am is just after midnight. This makes sense, because the first is very early 'afternoon' while the second is very early morning.
What Do These Terms Mean? “AM” and “PM” are both abbreviations of Latin terms and refer to a specific time of day: AM (ante meridiem) means “before noon,” so it refers to the morning. PM (post meridiem) means “after noon,” so it refers to any time after midday.
There are no standards established for the meaning of 12am and 12pm. It is often said that 12am Monday is midnight on Monday morning and 12pm is midday. This puts all the times beginning with 12 and ending with am in the same one-hour block, similarly with those ending with pm.
12:00AM is the start of the day, so midnight of the day before. How does the 12 hour clock time format work? The 12 hour clock runs as follows: 12:00AM, 1:00AM….
The day runs from midnight to midnight and is divided into 24 hours from 0 (midnight) to 23. Time is shown in hours and minutes since midnight.
The afternoon is the time of day that starts mid-day and ends in the evening. If you have an afternoon appointment, it's probably some time between 12:00 and 5:00 p.m. It's pretty much agreed that the afternoon begins after noon, or 12:00 p.m., but when the afternoon ends and evening begins is a bit more vague.
It is a midday.
A twelve-hour clock shows 12: 00 at midnight and 12: 00 at midday. A 24-hour clock shows from 0: 00 to 23: 59: 59. We call midnight as in a location the time is six hours after sunset and six hours before sunrise .
What does “a.m.” mean? The term we associate with the morning, a.m., is an abbreviation of the Latin phrase ante merīdiem meaning “before midday.”
Time of the day is divided in two halves (24hour= 12 hours before midday + 12 hours after midday) so the 11 AM is 11th hour before midday as clock strikes 12 again it changes to PM (after midday) so it's 12 PM after 11 AM and 12 AM after 11 PM.
There are two ways of telling the time: The 12-hour clock runs from 1am to 12 noon and then from 1pm to 12 midnight. The 24-hour clock uses the numbers 00:00 to 23:59 (midnight is 00:00).
The American Heritage Dictionary of the English Language states "By convention, 12 AM denotes midnight and 12 PM denotes noon. Because of the potential for confusion, it is advisable to use 12 noon and 12 midnight."
Put in simple terms, it does not. Common fallacy. AM stands for ante meridiem (before noon). PM stands for post meridiem (after noon).
It's all because of the conventions used with the "12-hour clock." 12:00 am is usually taken to mean midnight (and 12:00 pm is noon). At 59 minutes past midnight it is therefore 12:59 am, but a minute later it's 1:00 am.