Which date system does VBA recognise/default to?

Question

I\'m writing a vba subroutine in excel to store all date values between 2 dates in a single dimension array and then check for each value in a range on another sheet.

Answer 1

To provide a solution to my example a colleague mentioned if you dim the date values as the date datatype the issues with the values going sheet -> vba -> sheet disappears.

Answer 2

In general, the date system in VBA is different than the date system in Excel. You can have these 3 date system options:

• Excel date
• Excel date with 1904 property
• VBA date

This is the difference:

The dates are converted to numbers. E.g., every date is converted to a number, but the starting number is a bit different.

• In Excel, the 1 is converted to 01.January.1900;
• In VBA, the 1 is converted to 31.December.1899;
• In Excel with 1904, the 1 is converted to 02.January.1904;

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The 1904 system (or its lack) is set per Workbook. Thus, if you have 2 workbooks in Excel, one with 1904 and one without it, it would recognize them correspondingly. The system is set in:

File > Options > Advanced > Use 1904 Date System

In general, if there is a chance, that someone somehow changes your workbook with the wrong system, consider adding this check at the openning of the workbook:

Private Sub Workbook_Open()    
    If ThisWorkbook.Date1904 Then
        MsgBox "System is 1904, consider some action!"
    End If        
End Sub

If you are wondering which system to choose - I can recommend never using the 1904.

• Story for the adding VBA to Excel and the 1904 problem