Four an' Twenty Day

Four an' Twenty Day

January 18
When England and Scotland switched from the Julian to the Gregorian calendar in 1752, 11 days were dropped to make up for the additional time that had accumulated during the use of the Julian calendar. Four an' Twenty Day (or Old Twelfth Day ) is a Scottish expression referring to the day on which Twelfth Night used to be celebrated before the switch.
SOURCES:
DictDays-1988, p. 43