如何在星期、日期、时间前加介词?

以下是初中阶段需要掌握的介词用法：
on + 具体的某一天
on Monday
on Christmas Eve
on a cold winter morning
on December 2nd
in用法
in the morning (evening/ afternoon)
in spring (summer/ autumn/ winter)
in December (month)
in 2012 (year)
at 用法
at noon (midday/ night)
at 7 o'clock (具体时间）
有last,next,tomorrow等修饰时,不需加介词,例如：
I'll be back tomorrow morning.