closing time (of a library, museum, etc.)
Used for the scheduled closing time of public facilities such as libraries, museums, and galleries. Not used for shops or restaurants; for those, 閉店時間 is more common.
The library's closing time is 8 p.m.
When closing time approaches, an announcement is made inside the facility.
閉店時間 is used for the closing time of shops, restaurants, and commercial establishments, while 閉館時間 is specifically for public facilities like libraries and museums.
Compound of 閉館 (closing of a public facility) + 時間 (time). The exact historical derivation is straightforward from the kanji meanings.