Henceforth vs Whenever - What's the difference?

As adverbs the difference between henceforth and whenever

is that henceforth is (formal) from now on; from this time on while whenever is at whatever time.

(-)

(formal) From now on; from this time on.

* William Shakespeare, Macbeth , Act I, scene II:

My thanes and kinsmen,/'Henceforth be earls, the first that ever Scotland /In such an honour named

I will try to do a better job, henceforth , now that I know the proper technique!

* henceforward

(-)

At whatever time.

Visit whenever you want to.

(Irish, US, colloquial) When.

Whenever you get into town, come by and see me.

Every time.

Whenever he has a pair of aces, his eyelids twitch.