A data processing unit includes: a data storage section; a data acquisition section that acquires the dates of multiple date items including date attributes; a date representing section that represents the dates of data in such a manner that the lapse of months from January to December is expressed circumferentially and the lapse of two or more years is expressed radially; a search-range representing section superposed on the date representing section and representing a sectored search range concentric with the date representing section so that the user can designate a search range, wherein the central angle of the sectored search range represents the range of date of search data and the radial thickness of the sectored search range represents the range of year of the search data; and a search section that searches for data having the date in the range designated in the search-range representing section from the date stored in the data storage section.