专题:
since then表示从那个时间点到现在的情况，一般用现在完成时，表示过去的某件事对现在还有影响。如：Ihave not gone there since then.从那以后，我从来没有去过那里。
since then一般用什么时态
since then意为 "从那时以来"，通常与动词的现在完成时连用，指从过去某一时刻起到现在为止的一段时间。
since then的用法例句：
Since then, he has developed another bad habit.
从那以后,他养成了另一种坏习惯。
He hasn't come close to those numbers since then.
自那以后，他从没有达到那赛季的表现。
Ah, times are greatly changed since then!'
“啊，从那时起，世道可变得多厉害呀！”
since的用法句型有哪些
since+时间点，要求谓语动词用现在完成时，而且必须是延续性动词。
since+一段时间+ago，要求谓语动词用现在完成时，而且必须是延续性动词。
since+从句，要求主句谓语动词用现在完成时，而且必须是延续性动词；从句谓语动词用一般过去时，而且是终止性动词。
It is/ has been +一段时间+since从句，意为“自从……以来已经（多久）了”。例句如下：
I have stayed in that country since 1995. 从1995年以来我就在那个国家了。
They have lived in that house since two years ago. 两年前他们就住在那座房子里了。
Lily has stayed at home since she left school. 莉莉离开学校之后就一直呆在家里。
It has been three months since he moved to this city. 他搬到这个城市已经三个月了。