Should I choose "am" or "PM" to set the alarm clock at 12 noon?

Should I choose "am" or "PM" to set the alarm clock at 12 noon?

12 at noon is am12
Indeed, many people think that 12 am is midnight, which is still controversial in English speaking countries
According to the Latin text, am = before noon; PM = post noon
So 12:00 at noon is 12 am [12:00 in the morning]
12:00 midnight is 12 pm
But strictly speaking, 12 o'clock is neither before nor after, so it's better to use non or midnight
The 24-hour system avoids this confusion

Why am in the morning and PM in the afternoon
O Latin abbreviation?

AM:ante meridiem
PM:post meridiem
Meridiem is the meridian. It's morning before the meridian, of course

What are the sources of AM and PM?

There is no deep source
They are just abbreviations of phrases:
a. M. = ante meridian = before noon
p. M. = post media (= afternoon) afternoon

How to read English am in the morning and PM in the afternoon

a. M. is the abbreviation of ante meridiem
p. M. is the abbreviation of post meridiem
When they appear in the form of abbreviations, they can be pronounced directly by reading the letters