Abstract: A calendar comprising two sheets with one laid flat against the other and the sheets being moveable one over the other. One of the sheets is an intended lower sheet and the other sheet is an intended upper sheet. One sheet bears the numbers “1” to “31” marked on it in order with uniform spacing between successive numbers. The other sheet bears markings with uniform spacing between them such that the numbers can be brought into registration with respective ones of the markings, successive markings being indicative of successive days of the week in cyclical fashion for at least a full five weeks, so that the number 1 on the sheet bearing the numbers can be brought into registration with any selected one of the markings representing any day of the week. Each month is represented by an indication on the sheet bearing the said markings adjacent to a marking indicative of that day of the week on which the first day of that month falls.