Excel Serial Date ↔ Unix Timestamp Converter
Convert Excel 1900/1904 serial dates and Unix seconds or milliseconds in both directions, with batch rows and an explicit UTC offset.
UTC: 1900 serial 25569 = Unix 0; 1904 serial 24107 = Unix 0. For dates from 1900-03-01 onward, the two serial systems differ by 1462 days.
Excel serial dates contain no timezone. This tool uses your explicit fixed UTC offset, without inferring daylight saving time; verify the offset for ambiguous or nonexistent local times. Modern Windows and Mac Excel generally use the 1900 system: check the workbook setting. Serial 60 in the 1900 system is the fictitious 1900-02-29 and returns an error. Negative serials extend the date arithmetic, although Excel cells may not display those dates. Precision is one millisecond.