Translation guide
The English phrase "ancient history" can refer literally to the historical period, or figuratively to something in the past that is no longer relevant or worth discussing.
Referring to the study or time period of ancient civilizations, typically before the Middle Ages.
Dismissing a past event or relationship as unimportant now, often used in personal contexts.
Literally 'a story of the past'. Commonly used to say something is water under the bridge or no longer an issue.
あの喧嘩はもう昔の話だよ。
That fight is ancient history now.
Do not translate the figurative sense of 'ancient history' directly as 古代史. That only means the academic subject. Use phrases like 昔の話 or 過去のこと instead.
He is majoring in ancient history at university.
A more general phrase meaning 'history of ancient times'. Slightly less formal than 古代史.
古代の歴史に興味があります。
I'm interested in ancient history.
Means 'a thing of the past'. Neutral and can be used in both personal and formal contexts.
その失敗はもう過去のことです。
That failure is ancient history.
Literally 'something that has ended'. Emphasizes finality, often used to dismiss a topic.
それはもう終わったことだから、気にしないで。
That's ancient history, so don't worry about it.
Emphatic colloquial expression meaning 'way back when' or 'ages ago'. Used humorously or dramatically.
そんなの昔の昔の話だよ。
That's ancient, ancient history.