'Clear' days. The four days in each month on which festivals could be held according to the lunar calendar. These are the days of the new, full and half-moons, i.e. the 1st, 7th or 8th, 15th, and 22nd or 23rd. Other days are known as ke-no-hi and were seldom used for festivals. After the solar calendar was adopted in 1872 many festivals were re-scheduled, regardless of the hare/ke distinction, though local festivals often still keep to the lunar calendar.
See Nenchu gyoji.
A Popular Dictionary of Shinto. Brian Bocking.