1)在具体某一天：on March the first(on March 1)
2)在星期名称前：on Friday,on Sunday
3)在某一天的上午,下午或晚上：on Friday morning
4)在固定短语中：on time准时
5）on+动名词.表示“一.就...”：On hearing the good news,they jumped with joy.
他们一听到这个好消息就高兴得跳了起来.