Abstract: A calculator for use in planning the orderly production of swine throughout a calendar year. The calculator includes a base and a disc rotatably mounted on the base. A circular scale is formed on the base around the outer edge of the disc. This circular scale has 365 equally spaced marks numbered in sequence around the scale. A second circular scale is formed on the outer edges of the disc and it has indicia indicating the months of the year with each month having indicia indicating the days of the month. The sequence of the indicia on the disc scale run in the opposite direction of rotation to the sequence of the indicia on the base scale. An alignment indicator is provided overlying the scales and aligned with the indicia number 1 on the base scale. A series of spaced, circumferentially extending bands are superimposed on the indicia of the base scale.