英语 in advance 和ahead of time .ahead of schedule.区别.请问他们之间的区别.举几个例子.

剑桥高级学习词典
in advance
in advance
before a particular time, or before doing a particular thing:
If you're going to come, please let me know in advance.
ahead of time
ahead of time MAINLY US
in advance:
Let's meet for lunch. I'll call you ahead of time to fix up exactly when and where.
ahead of schedule
ahead of schedule
early:
We expect the building work to be completed ahead of schedule.

首先，三者都有“提前”的意思。
in advance 常置于句尾,常常是提前做某事。
例：It is cheaper if you book the tickets in advance.
ahead of time 强调的是提前了具体的某一小个时间段，
例：He arrived ahead of time, and had to wait.
ahead of schedule 强调的是比原计划，原进度提前了，句子的主题是一项任务类的事情
例：We finished the project ahead of schedule.

in advanced应用于所有的语气,表示“事先,提前”的意思!Tell me in advance!提前给我说!ahead of time这里有一个时间点,“在这个时间点之前”,比如俩人说好了八点见面,为了保险起见,一个会说：I'll phone you ahead ...