An electronic device used for writing memos includes a storage unit, a display unit, a touch input unit, and a processor. The storage unit is used for storing an electronic calendar and a memo file written by a user. The touch input unit senses touch input of handwritten content on the displayed electronic calendar by the user and generating signals associated with the user's touch input, and recognizes handwritten content of the user according to the generating signals. The processor includes an identification module and a memo adding module. The identification module determines a date associated to the created handwritten content according to the generated signals. The memo adding module automatically adds the recognized handwritten content to the memo file stored in the storage unit of the determined date. A method for writing memos is also described.