L.2.16.9.1 Date Conversion for Serial Values
All date values stored in cells within a SpreadsheetML file are stored in the ISO 8601 format.
For compatibility, a SpreadsheetML application can interpret serial-number values in cells or in formulas as dates. This subclause describes how serial number values can be converted to date values depending on the compatibility mode.
A date that can be interpreted as a numeric value is a serial value. This is made up of a signed integer date component and an unsigned fractional time component. Going forward in time, the date component of a serial value increases by 1 each day. A serial value represents a UTC date and time, and, as such, has no timezone information.
Three different bases can be used for converting dates into serial values:
In the 1900 date base system, the lower limit is January 1, -9999 00:00:00, which has serial value -4346018. The upper-limit is December 31, 9999, 23:59:59, which has serial value 2,958,465.9999884. The base date for this date base system is December 30, 1899, which has a serial value of 0. In the 1900 backward compatibility date-base system, the lower limit is January 1, 1900, 00:00:00, which has serial value 1. The upper limit is December 31, 9999, 23:59:59, which has serial value 2,958,465.9999884. The base date for this date base system is December 31, 1899, which has a serial value of 0. In the 1904 backward compatibility date-base system, the lower limit is January 1, 1904, 00:00:00, which has serial value 0. The upper limit is December 31, 9999, 23:59:59, which has serial value 2,957,003.9999884. The base date for this date base system is January 1, 1904, which has a serial value of 0.
For the 1900 date base system:
The serial value -2338.0000000… represents 1893-08-05 The serial value 2.0000000… represents 1900-01-01 The serial value 3687.0000000… represents 1910-02-03 The serial value 38749.0000000… represents 2006-02-01 The serial value 2958465.0000000… represents 9999-12-31
For the 1904 backward compatibility date base system:
The serial value -3800.0000000… represents 1893-08-05 The serial value 0.0000000… represents 1904-01-01 The serial value 2225.0000000… represents 1910-02-03 The serial value 37287.0000000… represents 2006-02-01 The serial value 2957003.0000000… represents 9999-12-31