Important: To ensure that year values are interpreted as you intended, type year values as four digits (for example, 2001, not 01). 1,462 days is equal to four years and one day (which includes one leap day). Conversely, the serial value of a date in the 1904 date system is always 1,462 days less than the serial value of the same date in the 1900 date system.

The difference between the two date systems is 1,462 days that is, the serial value of a date in the 1900 date system is always 1,462 days greater than the serial value of the same date in the 1904 date system. For example, Jcan have two different serial values, depending on the date system that is used. The following table shows the first date and the last date for each date system and the serial value associated with each date.īecause the two date systems use different starting days, the same date is represented by different serial values in each date system. Originally, Excel for Mac was based on the 1904 date system, because it enabled better compatibility with early Macintosh computers that did not support dates before January 2, 1904, and therefore it became the default date system. Originally, Excel for Windows was based on the 1900 date system, because it enabled better compatibility with other spreadsheet programs that were designed to run under MS-DOS and Microsoft Windows, and therefore it became the default date system. The default date system for Excel for Windows is 1900 and the default date system for Excel for Mac is 1904. Both Excel for Mac and Excel for Windows support the 19 date systems.

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