What do PM and AM mean?

If you have never been to America, it will be hard for you to tell exactly what time it is, that is due to two mysterious letters: AM and PM. The thing is that there is a 12-hour clock in the United States, instead of 24-hour clock day that people are used to in Russia.

That's why 24 hours of the day are divided into two periods: from12 midnight to 12 noon and from 12 noon 12 midnight. In order to avoid confusion AM and PM abbreviations are used:

• AM — Ante Meridiem. This latin phrase is translated as "before midday".
• PM — Post Meridiem. This phrase is translated as "after midday".

Thus, AM is the time from 00:00 to 12:00; PM - from 12:00 to 00:00. Examples: 1 a.m. refers to the nighttime , and 1 p.m. refers to the daylight time.

However, 12 a.m does not always denote noon, so 12 p.m. does not always denote midnight. The fact is that many American certified guidelines suggest that it is better to designate midnight in the format of 11.59 p.m. - Thus, the end of one day is emphasized. The beginning of the next day is recommended to be designated in the format of 12.01 a.m. These recommendations are used when scheduling traffic and legal transactions in the United States of America.

In writing AM and PM can be designated in a number of ways: with the help of dots -a.m. and p.m.; without dots using lower case - am and pm; without dots using capital letters - AM and PM. All three abbreviations' variants are correct.