12 noon. (This is one question that not just Chinese, but westerners are often confused. There are many web sites that talks about this. We have had a few here, but I don't know where they are.)
Officially at mid-day, it is 12 noon.
For your interest:
(1)
http://en.wikipedia.org/wiki/12-hour_clockThe most common convention is to assign 12 a.m. to midnight and 12 p.m. to noon, defining both half days to have a closed (inclusive) beginning and open (exclusive) end; however, "12 noon" and midnight more clearly and correctly express these times.
(2)
http://wwp.greenwichmeantime.com/info/noon.htmAM and PM start immediately after Midnight and Noon (Midday) respectively.
This means that 00:00 AM or 00:00 PM (or 12:00 AM and 12:00 PM) have no meaning.
Every day starts precisely at midnight and AM starts immediately after that point in time e.g. 00:00:01 AM (see also leap seconds)
To avoid confusion timetables, when scheduling around midnight, prefer to use either 23:59 or 00:01 to avoid confusion as to which day is being referred to.
It is after Noon that PM starts e.g. 00:00:01 PM (12:00:01)
google一下长知识了……
英文过了6级就没怎么碰过了