And what do you do in the evening?And what do you do an the weekend?

at the weekend 强调的是一个具体的时间,在具体的时间点前用at,是它的一般用法.如：
I don't work at the weekend.

但如果强调的是一个特定的周末,就不能用at而要改为on.
如：Jack was killed on the weekend of May Ist,1987.谢谢指点呀，那in呢？没有in the weekend这种说法。