weekdays前面介词可以用on也可以用at。用介词at为英国英语，用on为美国英语。例句：They like to go fishing on the weekend.他们周末喜欢钓鱼玩。Traffic on the roads is heaviest at weekends.周末的交通最为繁忙。
例句
Mrs Simpson comes in on weekdays to do for us.
辛普森夫人周日替我们料理家务。
I'm busy on weekdays. May I see you on Sunday?
我平时很忙，我可以在周日与你见面吗？
The library is open on weekdays only.
这个图书馆星期一至星期六都开放。
I don't stay out late on weekdays.
工作日的时候我不在外面呆得很晚。