Is noon 12am or 12pm?
'Noon' means 'midday' or 12 in the afternoon. The standard way of writing this therefore would be 12pm.
However, there are ways to avoid the confusion completely: you could write 12 noon or 12 midnight instead.
Alternatively, you could use the 24-hour clock system, where 12:00 is noon and 24:00 (or 00:00) is midnight.
What does pm mean?
While most people would use 12pm to mean 12 noon, technically this isn't quite right.
The abbreviation am stands for ante-meridiem (before the Sun has crossed the meridian line), and pm stands for post-meridiem (after the Sun has crossed the meridian line).
At 12 noon, the Sun is at its highest point in the sky and directly over the meridian. It is therefore neither 'ante' (am) nor 'post' (pm) meridiem.
If all these questions about time have got you in a spin, why not visit the Royal Observatory, where many more mysteries of time await...