Henceforth is defined as starting now.
(adverb)When you change your name from Smith to Jones after you get married, this name change is an example of when you might say 'Henceforth, I shall be called Jones."
See henceforth in Webster's New World College Dictionary
adverb
Origin: ME hennesforth: see hence & forth
See henceforth in American Heritage Dictionary 4
adverb
Learn more about henceforth