Formal, somewhat literary expression for 'from this point forward'. Often used in official announcements, legal documents, or solemn declarations. In everyday speech, これから or 今後 are more common.
From now on, this rule must be strictly observed.
Please be mindful of your conduct hereafter.
今後 is the standard, neutral word for 'from now on' or 'in the future'. 自今 is more formal and literary, often with a sense of a new beginning or resolution.
これから is the everyday conversational equivalent. 自今 is much more formal and rarely used in speech.
henceforth; hereafter
Formal, somewhat archaic kanji spelling. Most commonly encountered in written or official contexts.
Archaic variant; rarely used in modern Japanese.
Contains out-dated kanji usage; not used in contemporary writing.
Compound of 自 (from) and 今 (now). The exact historical derivation is uncertain, but it has been used in formal written Japanese to mean 'from this moment onward'.