Runic calendar

Special days like solstices, equinoxes, and celebrations (including Christian holidays and feasts) were marked with additional lines of symbols.

On another line, many of the days were marked with one of 19 symbols representing the 19 Golden numbers, for the years of the Metonic cycle.

Because this system needed 19 runes to represent the 19 golden numbers which stood for the 19 years of the perpetual calendar's cycle, the Younger Futhark was insufficient, having only 16 characters.

In 1636, Ole Worm documented the Younger Futhark numeral system, including these three characters, in his Runir seu Danica literatura antiquissima (Runes: the oldest Danish literature).

[1] A version using the Latin alphabet for weekdays and Arabic numerals for the golden numbers was printed in 1498 as part of the Breviarium Scarense.

Younger furthark runic calendar.
Runic calendar from the Estonian island of Saaremaa with each month on a separate wooden board.
Primstav from Hallingdal with coat of arms of Norway , 17th century.