In 1961, new parents David and Doris Wagner had a baby and Doris went on the birth control pill, just approved by the FDA the year before. Quickly though, Doris and David realized that it was too easy to forget a day and not realize it, so they invented a calendar dispenser that was the basis for the compact-shaped dial packs still common today.
From the National Museum of American History:
(David Wagner's) background in engineering helped him to build a prototype dispenser using just "a ¼' drill, a fly cutter to be used in the drill, paper, a saw, a staple, pencil, double-faced transparent tape, several drill bits, a snap fastener that [he] took off a child's toy, and several flat, clear sheets of either acrylic or polycarbonate plastic." In choosing a shape, he made the case "indistinguishable from a lady's cosmetic 'compact' and adapted to be carried among the personal effects of a lady in a purse without giving a visible clew [sic] as to matters which are no concerns of others."