An object of the present invention is to convert a voice to a character string and output attribute data associated with the character string. The central controller of the data processing apparatus converts a voice entered from the voice input unit through the voice/character code conversion processing to a character string. Then, any date and time part of the character string are detected through the date detection processing and the time detection processing and the detected date and time part are converted to predetermined date and time words through the date conversion processing and the time conversion processing. Finally, the converted date and time are associated to a voice and a character string as attribute data through the monitor controlling and stored in the schedule memory as schedule data. Consequently, the date and time are associated to a voice and a character string automatically. The current date and time clocked by the clocking unit are also used as such attribute data, so that either of any detected date and time part or the current date and time are selected and used.