From this or that time on.
Usually used by 12 year olds to sound more educated when writing an essay for school.
Henceforth, parties which fail to get 5% of the vote will not be represented in parliament.
From this time on or from that time on.
The company announced that it would henceforth charge royalties
The smartest way of saying "I can't/I cannot"
"The way I would write I can't in an essay? 'Henceforth I am unable to can'"