OK, you can adjust the mapping of day numbers in the options dialog to adjust
this spreadsheet document. Within this document everything will work as expected.
rbc wrote:I should ask: how do I add four years to the date? I have them in DD/MM/YYYY format.
This is a legitimate question. When you copy day numbers between this document with 1904 setting and other documents with standard setting, the days will be 1462 days off (difference between 1899-12-30 and 1904-01-01). First of all, the formatting of day numbers does not make any difference at all. You may even format them as currency values without losing any information and all calculation working correctly.
Enter number 1462 in a cell and copy that cell.
Select one range of date cells and paste-special (Ctrl+Shift+V).
In the upcoming dialog choose options "Numbers" and "Add" before hitting OK.
This will add the value of the copied cell to all numeric cells within the selection.