11 PM (23:00). Late evening, just before midnight; often used for late gatherings or last train timings.
飲み会が盛り上がって、気づいたら２３時を過ぎていた。
The drinking party got lively, and before I knew it it was past 11 PM.
２３時発の最終バスに間に合うように出発した。
We left to make it to the last bus departing at 11 PM.
図書館は平日は２３時まで開いています。
On weekdays the library is open until 11 PM.