Extension of date-time serial numbers

[elsaminsut]

Request

Right now a date-time serial number is only valid between 1 and 2958466, corresponding to the number of days between 31-12-1899 and 31-12-9999. This is the current behavior of Excel, but other spreadsheets are not limited by this. Adding support for negative serial numbers and extending the upper limitation can make IronCalc work with most dates.

Examples

Google Sheets

• Start date: 01-01-100 (serial number = -657,434)
• End date: 12-31-99999 (serial number = 35,830,290)

LibreOffice

• Start date: 15-10-1582 (serial number = -115,858, see Gregorian Calendar )
• End date: 12-31-99999 (serial number = 35,830,290)

Solution

• Change start date to 01-01-100 (serial number = -657,434) and end date to 12-31-99999 (serial number = 35,830,290)
• Keep 31-12-1899 as serial number 1 for compatibility reasons, any dates before that will have negative values