Convert serials from Mac workbooks that use the 1904 date system, 1,462 days apart
Runs in your browser. Nothing you type is sent anywhere. Updated on 24 Oct 2026.Dates that jump by four years and one day when a sheet is copied between workbooks are almost always the 1904 date system. Older Mac workbooks count from 1 January 1904, Windows from 1900, and the same day differs by 1,462 in serial number. This page starts in the 1904 system, converts either way, and shows the serial the other system would use.
Open the page with the 1904 (Mac) date system selected and 39267 entered.
Type a serial from the workbook that uses the 1904 system and read its date.
Switch to 1900 (Windows) to see the same number read the Windows way, 1,462 days apart.
Copy the corrected date, or convert a whole column on the List tab.
This converter reads an Excel date serial number and shows the calendar date, the weekday and the time, or takes a date and gives the serial Excel would store. Type 45292 to get 1 January 2024; type 2024-01-01 18:00 to get 45292.75. A number is read as a serial and anything else as a date, so there is no mode to set. Times can also be converted on their own: 18:30 is the fraction 0.7708333333.
Both of Excel's date systems are supported. The 1900 system, the default on Windows, counts 1 January 1900 as day 1. The 1904 system, used by older Mac workbooks and still selectable in Excel's options, counts 1 January 1904 as day 0. Microsoft documents the gap between them as 1,462 days, and the page shows the other system's serial for every result, which explains dates that are four years and one day out after copying between workbooks.
The 1900 system keeps a known mistake. Lotus 1-2-3 treated 1900 as a leap year, and Excel copied it for compatibility, so serial 60 is 29 February 1900, a day that never existed. The converter shows that date as Excel does and flags it. Serials 1 to 59 are one day earlier than a naive count from 30 December 1899 gives, and the weekday shown is the real one, not the one Excel's WEEKDAY function reports.
The rest of the article, and all 6 questions about Excel Date Serial Converter, are on the Excel Date Serial Converter page.
In the default 1900 date system, 45292 is Monday 1 January 2024. The number counts days, so 45293 is 2 January. In the 1904 date system the same number would be 1,462 days later, 2 January 2028, which is why knowing the workbook's date system matters.
The 1900 system counts from 1 January 1900 and is the Windows default. The 1904 system counts from 1 January 1904 and came from early Mac Excel. Microsoft documents that the same date's serial is always 1,462 higher in the 1900 system than in the 1904 system.
The time is the fraction after the decimal point: the share of a 24-hour day that has passed. 0.5 is noon, 0.75 is 18:00 and 0.7708333333 is 18:30. The converter rounds to the nearest millisecond and shows milliseconds only when they are not zero.
Yes. Paste the column into the batch box, one value per line. Numbers become dates and dates become serial numbers, in the date system you have chosen. Copy the result as tab-separated text and paste it next to the original column in your spreadsheet.
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