on the instant 和the instant的区别?

1.on the instant 立即,马上;
e.g.leave on the instant of six o'clock （ ie not a second later than six ）
六点整离开
2.the instant ...或者 the instant that ...一 ...就 ...；
e.g.I sent you the news the instant (that) I heard it.
我一听到此消息,便通知你了.