hour of the Rabbit; hour of the Hare
Archaic term for the time period around 6am, corresponding to the fourth of the twelve traditional Chinese hours. The exact span varies by system (e.g., 5-7am or 6-8am).
江戸時代には、卯の刻は明け六つとも呼ばれた。
In the Edo period, the hour of the Rabbit was also called 'ake-muttsu'.
From 卯, the fourth zodiac sign, and 刻, a temporal division. In traditional timekeeping 卯の刻 was the period around dawn; its exact clock length varied under the seasonal-hour system.