大多数不需要，但是,若是强调某一天时,可以加上冠词
weekend:What are you doing next weekend?你下周末打算干什么?
school day 前面也不需要：I can\'t play computer games on school days.我上学时不能打电子游戏.
It\'s a school day tomorrow,I can\'t stay up too late.明天我还要上学,所以不能睡得太晚.
But it\'ll be the weekend,sure you can have some fun.可是那是在周末,你难道就不能放松一下吗?
