The Problem Of Y10K (Year 10,000 Problem)

This problem can be seen in the spreadsheet program Microsoft Excel through at least the Office Excel 2007 release, which stores dates as the number of days since 31 December 1899 (day 1 is 1900-01-01), and the database program Microsoft Access, which stores dates as the number of days since 30 December 1899 (day 1 is 1899-12-31). In either application, a date value of 2958465 will be correctly formatted as "31 December 9999" but adding 1 to that to step over to the expected date of "1 January 10000" will cause a formatting error; in Excel 2000, for example, it will be displayed in the cell as a series of # characters. Excel also cannot automatically convert date-formatted strings such as "12/12/2007" to dates if the year exceeds 9999; "12/12/9999" is automatically converted to a date when entered into a cell, but "12/12/10000" is not. The Long Now Foundation ran into this limitation of Excel during the design of the 10,000 year clock.^[2]

SAP R/3 handles date variables as strings of 8 characters (YYYYMMDD).^{[citation needed]}

The open source OpenOffice.org Calc program is able to display dates beyond the year 9999 correctly with five digit years, but at least through version 2.4 falls victim to the Year 32,768 problem: "31 December 32,767" is the highest available date it can properly display. 32767, or 2¹⁵-1, is the highest positive number that can be represented using a 16-bit signed integer, adding one to this value causes it to overflow, and Calc interprets the year as a large negative number, "1 January -32768".

The GNU Fortran compiler, g77, makes reference in run-time environment limits to year 10000 (Y10K) problems when using intrinsic functions with this compiler suite. The problem is simply stated as, "Most intrinsics returning, or computing values based on, date information are prone to Year-10000 (Y10K) problems, due to supporting only 4 digits for the year." The failure mode suggested in all of the intrinsic functions is that, "Programs making use of this intrinsic might not be Year 10000 (Y10K) compliant. For example, the date might appear, to such programs, to wrap around (change from a larger value to a smaller one) as of the Year 10000.