The second period, marked pm, covers the 12 hours from noon to midnight. The abbreviations am and pm derive from Latin: AM = Ante meridiem: Before noon. PM = Post meridiem: After noon.
We associate P.M. with the afternoon and evening. P.M. is an abbreviated term for 'Post Meridiem,' which implies afternoon or after midday. In a 12-hour clock, these are used as time indications centered around noon.
As the day begins at midnight, midnight must be 12am. The moment of noon is in the first second, consequently minute and hour of the afternoon therefore noon must be 12pm.
“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.
P.M. is used to represent evening and not morning. P.M is the time from noon to midnight. It is Pre Midnight or the time before midnight.
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.”
For example, “Good morning” is generally used from 5:00 a.m. to 12:00 p.m. whereas “Good afternoon” time is from 12:00 p.m. to 6:00 p.m. “Good evening” is often used after 6 p.m. or when the sun goes down.
AM and PM are the abbreviated terms for Ante meridiem and Post meridiem which means before noon or midday and afternoon or midday respectively. 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 designated with PM.
afternoon - the time between 12:00 p.m. and 5:00-6:00 p.m. evening - roughly the time between 5:00 or 6:00 p.m. and 8:00 or 9:00 p.m.
In the 12-hour clock, system AM and PM are used to prevent this ambiguity. Accordingly, the morning is 8 am and evening is 8 pm.
Midday and midnight conventions
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.
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.
The word noon is derived from Latin nona hora, the ninth canonical hour of the day, in reference to the Western Christian liturgical term none, one of the seven fixed prayer times in traditional Christian denominations.
12 Noon | 12 Midday | 12 Midnight
To avoid confusion, it is better to use the 24-hour clock, when 12:00 is 12 noon and, for example, 24:00 Sunday or 00:00 Monday both mean 12 midnight Sunday/Monday.
So, 7 o'clock in the morning is 7 a.m. 'p.m.' stands for post meridiem, which means after midday. Thus, 'p.m.' is used between 12 o'clock noon to 12 o'clock midnight. So, 7 o'clock at night is 7 p.m.
Late- afternoon: 3-6 p.m. Evening: 6-9 p.m. Late at night: Midnight-6 a.m.
evening = sunset until you go to bed (or 10pm/11pm).
8pm is in the evening.
Finally, note that while in the US we use a 12-hour clock, some countries use a 24-hour clock, or military time. Therefore, one hour past noon is 1:00 pm on a 12-hour clock, but 13:00 using a 24-hour clock.
Daytime is from sunrise (this varies, but we can say approximately 6am) to sunset (we can say approximately 6pm). Night-time is from sunset to sunrise. Every day starts precisely at midnight. AM (ante-meridiem = before noon) starts just after midnight.
Afternoon 12:01 p.m. to 5:00 p.m. Late afternoon 4:00 pm to 5:00 pm. Early evening 5:00 pm to 7:00 pm. Dusk around sunset Evening 5:00 pm to 9:00 pm. Late evening 9:00 p.m. to 11:00p.
The 12-hour clock divides the 24-hour day into two periods. am stands for the Latin ante meridiem, translating to "before midday". This is the time before the sun has crossed the meridian. pm stands for post meridiem or "after midday" – after the sun has crossed the meridian.
Late- afternoon: 3-6 p.m. Evening: 6-9 p.m. Late at night: Midnight-6 a.m.