Dates and Times

As a date and/or time is represented by a number, a date/time serial value shall be stored in XML as the unformatted text form of that number, as accurately as possible.

The date base system is recorded in the Workbook part's XML by the presence or absence of the @date1904 attribute of the <workbookPr> element. A value of 1 for this attribute indicates 1904.

example: :

1900: <workbookPr showObjects="all"/>1904: <workbookPr date1904="1" showObjects="all"/>