What does a "Twelfth Night" mean? Almanac definition

from list serv of Old Farmer's Almanac (www.almanac.com/ )

Twelfth Night is an English folk custom that marks the end of Christmas merrymaking and, in the ancient Celtic tradition, the end of the 12-day winter solstice celebration. On Twelfth Night, it was customary for the assembled company to toast one another from the wassail bowl. In Old English, wassail means "Be in good health," but the term also was applied to the drink itself (usually spiced ale).