Article ID: 180162 - View products that this article applies to.
This article was previously published under Q180162
Microsoft Excel supports two different date systems: the 1900 date system and the 1904 date system. This article describes the two date systems and the problems that you may encounter when you use workbooks that use different date systems.
The 1900 Date SystemIn the 1900 date system, the first day that is supported is January 1, 1900. When you enter a date, the date is converted into a serial number that represents the number of elapsed days since January 1, 1900. For example, if you enter July 5, 1998, Microsoft Excel converts the date to the serial number 35981.
By default, Microsoft Excel for Windows and Microsoft Excel for Windows NT use the 1900 date system. The 1900 date system allows greater compatibility between Microsoft Excel and other spreadsheet programs, such as Lotus 1-2-3, that are designed to run under MS-DOS or Microsoft Windows.
The 1904 Date SystemIn the 1904 date system, the first day that is supported is January 1, 1904. When you enter a date, the date is converted into a serial number that represents the number of elapsed days since January 1, 1904. For example, if you enter July 5, 1998, Microsoft Excel converts the date to the serial number 34519.
By default, Microsoft Excel for the Macintosh uses the 1904 date system. Because of the design of early Macintosh computers, dates before January 1, 1904 were not supported; this design was intended to prevent problems related to the fact that 1900 was not a leap year. Note that if you switch to the 1900 date system, Microsoft Excel for the Macintosh does support dates as early as January 1, 1900.
The Difference Between the Date SystemsBecause the two Date Systems use different starting days, the same date is represented by different serial numbers in each date system. For example, July 5, 1998 can have two different serial numbers.
The difference between the two date systems is 1,462 days; that is, the serial number of a date in the 1900 Date System is always 1,462 days greater than the serial number of the same date in the 1904 date system. 1,462 days is equal to four years and one day (including one leap day).
Serial number Date system of July 5, 1998 ---------------------------------- 1900 date system 35981 1904 date system 34519
Setting the Date System for a WorkbookIn Microsoft Excel, each workbook can have its own date system setting, even if multiple workbooks are open. You can set the date system for a workbook by following these steps:
Problems Linking and Copying Dates Between WorkbooksIf two workbooks use different date systems, you may encounter problems when you link or copy dates between workbooks. Specifically, the dates may be shifted by four years and one day.
To see an example of this behavior, follow these steps:
Correcting Shifted DatesIf you link from or copy dates between workbooks, or if you change the date system for a workbook that already contains dates, the dates may be shifted by four years and one day. You can correct shifted dates by following these steps:
If you are using a formula to link to a date in another workbook, and if the date returned by the formula is incorrect because the workbooks use different date systems, modify the formula to return the correct date, for example:
In the formulas, 1,462 is added or deleted from the date value.
More Information in the Microsoft Knowledge BaseThe Microsoft Knowledge Base contains several other articles that have information about using the 1900 date system and the 1904 date system in Microsoft Excel. These articles are listed as follows:
(http://support.microsoft.com/kb/274277/EN-US/ )MacXL: Chart Axis May Be Four Years Early After You Format Scale
(http://support.microsoft.com/kb/214318/EN-US/ )XL2000: Chart Axis May Be Four Years Early After You Format Scale
(http://support.microsoft.com/kb/177172/EN-US/ )XL97: Chart Axis May Be Four Years Early After You Format Scale
(http://support.microsoft.com/kb/175753/EN-US/ )XL: DATE Function May Return #NUM! Error When Year Is 0-3
(http://support.microsoft.com/kb/157035/EN-US/ )XL: Date Returned in a Macro Is Four Years Too Early
(http://support.microsoft.com/kb/156987/EN-US/ )XL: Sheet Protection Does Not Disable Options Settings
Article ID: 180162 - Last Review: January 22, 2007 - Revision: 2.3
Retired KB Content Disclaimer
This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.