1、At 12 o'clock。

　　I have to be at school all day and I have lunch at 12 o'clock in the dining hall.

　　我整天都待在学校，中午12点在食堂吃午饭。

　　2、12 noon

　　Our team of experts will be on hand to offer help and advice between12 noon and7pm daily.

　　每天中午12点到下午7点，我们的专家小组将随时提供帮助和建议。

　　3、12 am.

　　Sometimes I need to work from 4 am to 12 am.

　　有时我需要从早上4点一直工作到中午12点

　　4、twelve noon.

　　You can check out any time before twelve noon.

　　中午12点以前任何时间都可以办理。