noun
Refers to the deepest, quietest part of the night, often with a spooky or eerie connotation. Commonly used in expressions like 丑三つ時.
丑三つ時になると、町は静まり返る。
At the dead of night, the town falls completely silent.
怪談では、丑三つに幽霊が出ると言われる。
In ghost stories, it's said that ghosts appear at the dead of night.
noun
third quarter of the ox's hour (around 2-2:30am or 3-3:30am)
Archaic timekeeping term; the original meaning referring to a specific period in the old Japanese temporal system. Now only encountered in historical contexts.
See also: 丑の刻
江戸時代の丑三つは、現代の午前2時から2時半頃にあたる。
The third quarter of the ox's hour in the Edo period corresponds to around 2:00–2:30 AM today.
丑の刻 refers to the entire ox's hour (1–3 AM), while 丑三つ specifically denotes the third quarter of that hour, often used in the phrase 丑三つ時 for the dead of night.
From the old Japanese timekeeping system where the ox's hour (丑の刻) was divided into four quarters. 丑三つ literally means 'ox third', indicating the third quarter. The association with the dead of night and supernatural themes developed later.