The calendar is formed of a flat sheet (1) possessing a straight base line (2) from which stand two parallel side edges (3,4) at right angles. The distance between the side edges determines the width of the sheet. Fold lines (5-10) between the side edges are at right angles to the base line and extend the full height of the sheet. Connecting elements in the form of overlapping parts (17) on the side edges join the sheet's side edges to a cylindrical column standing on the base line. Two adjacent fold lines define a written box (13-16).
