The wooden calendars or runic calendars reflect the popular system of chronology. The earliest information on the Estonian runic calendar goes back to the Hjärne's chronicle from the second half of the 17th century and runs as follows:
"In the county of Läänemaa I have seen that Estonians have /wooden/ sticks on which they have notched all the days of the /whole/ year together with the fixed holidays; without doubt they have taken this custom over from the Swedes inhabiting the nearby islands, where this custom is generally spread."
The runic calendar originates from Scandinavia. However, no too great importance should be ascribed to it in the Estonian system of chronology, as in all probability it was used by part of the Estonians only.
According to their form runic calendars fall into two large groups:
The main row of the Estonian runic calendar contains seven recurring signs, which are the seven first characters of the runic alphabet. In simpler calendars weekdays are cut out as similar short lines and Sundays are marked by crosses. The direction in which they are to be read can be guessed on the basis of the position of the special signs added to fixed holidays - these stand above the main row. Usually a runic calendar is read from left to right.
Holidays can also be made prominent by adding words to them instead of special signs or by using both ways, as exemplified by the St. Anthony's Day is marked in the runic calendar displayed here. There are differences between calendars in marking holidays both in the choice of the days regarded as worth indicating and in the way of denoting them. The signs used differ widely - from simple lines to sophisticated pictures. The usual sign of a holiday is a stylized depiction of some object. For example, a Catherine-wheel marks St. Catherine's Day (November 24th), a sprouting ear of corn indicates St. Eric's Day (May 18th), a tree with upward reaching branches denotes the ploughing day (April 14th), and a tree with drooping branches stands for October 14th, the day when leaves turn yellow on trees.