Apocalypse (Greek: apokalypsis, an "unveiling of secrets") is not an event, but a text that contains prophesies concerning God’s future intervention, and apocalypticism is a reference for attitudes and worldviews in biblical and non-canonical texts that share concepts in the belief that the God of Israel will intervene in human history one more time to address perceived ills of society.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1801/biblical-apocalypse/.