不是时间副词,是形容词性短语,例如:

1、He was injured early on and didn't last the match.他开赛后不久就受了伤,没法坚持到底。

2、Share prices fell early on but rose again late in the day.那天股票价格起先跌了,临近收盘时又涨了。

3、I knew quite early on that I wanted to marry her.我老早就知道我想娶她。