in+ 具体的年 / 月/季节,句子用可用过去时或一般现在时.这要看句子所要表达的意思.如
I was born in 1994.
It often snows in November.
in+时间段用于将来时.表示在这段时间后.
for后只加时间段用于一般过去时或现在完成时.如 He worked as a reporter for two years but now he is a lawyer.
He has been ill for two weeks.
since后只加时间点,如since last year.since two years ago .句子用现在完成时.如
I have lived here since I came here.