<60 days: Short-term employment income is exempt from tax

60~183 days: Employment income is taxed at 15% or resident rates, whichever gives rise to higher tax

more than 183 days: All income is taxed from 0% to 22%

应该没有2年这种说法，你朋友的情况应属于一般性的，也即上面的第三种缴税方式吧

看看官方网站的说法，应该可以找到你要的信息，good luck!