just at the right time; not a bit earlier or later
Related Translations:
先: 名词1.(时间或次序在前的) earlier; before; first; in advance 短语和例子有言在先 make clear beforehand; 争先恐后 strive to be the first and fear to lag behind; 你不必先付款。 you don't have to pay in advance. 你先拟个提纲再写。 m