Abstract: A perpetual calendar in the form of a desk calendar or wall supporting calendar including a front panel with a window cutout revealing a laterally movable slide having a projecting tab thereon engageable with notches or seats to properly locate the slide in relation to the window and maintain the slide in position. The calendar also includes printed indicia above the window opening indicating the days of the week and printed indicia below the window opening indicating the years. The slide includes indicia indicating the date of the month and additional indicia indicating the month of the year thereby providing easily adjusted indicia which can be readily observed to provide a calendar which will properly indicate the day of the week, the month, the date of the month and the year for many years.