page in history; historical event; old news
Used figuratively for a notable event that will be remembered, or for something already in the past. The 'old news' sense is often in negative or dismissive contexts.
This discovery will be recorded as a page in history.
That scandal is already old news.
Kanji numeral variant; slightly more formal or literary.
A set phrase combining 歴史 (history) and １ページ (one page), literally 'one page of history'. The figurative use is straightforward.