U+16EF Runic Tvimadur Symbol

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A Runic calendar (also Rune staff or Runic almanac) is a perpetual calendar, variants of which were used in Northern Europe until the 19th century. A typical runic calendar consisted of several horizontal lines of symbols, one above the other. Special days like solstices, equinoxes, and celebrations (including Christian holidays and feasts) were marked with additional lines of symbols.

Runic calendars were written on parchment or carved onto staves of wood, bone, or horn. The oldest one known, and the only one from the Middle Ages, is a staff from Nyköping, Sweden, believed to date from the 13th century. Most of the several thousand which survive are wooden calendars dating from the 16th and the 17th centuries. During the 18th century, Runic calendars had a renaissance, and calendars dating from around 1800 were made in the form of brass tobacco boxes.

The calendar is based on the 19 year-long Metonic cycle, correlating the Sun and the Moon, but the calendar does not prove knowledge of the length of the tropical year or of the occurrence of leap years. The two sliding halves are aligned and set at the beginning of each year by observing the first full moon after the first new moon after the winter solstice. The first full moon also marked the date of Disting, a pagan feast and a fair day also known as Thing of all Swedes.