1、since作介词时，后接表示过去时间点的名词、代词、动名词；作连词时，后接一般过去时的从句；在含有since的句子，谓语动词用现在完成时。例：Since last seeing you ,I have been ill.

I have been studying English since I was four years old.对since的句子提问用how long.

2、for后跟时间段。例：He has been surfing the Internet for about 3 hours.

3、during后跟时间段。例：During the summer holidays we went swimming every day.

4、in后面跟时间段，并且是表示年，月。例：I won't do back to my home in a year.

5、at后跟时间点，比如六点钟：at six o'clock.

6、on是指具体到某一天，例：on August 19th在8月19日。