VB Code:
Sub DateThinger()
Dim Cntr As Long
Dim i As Long
Dim K%
Cntr = 0
For i = 1 To 65536
ActiveSheet.Range("$a$" & i).Select
ActiveCell.Value = DateAdd("d", Cntr, Date)
For K = 1 To 255
Cntr = Cntr + 1
ActiveCell.Offset(0, K).Value = DateAdd("d", Cntr, Date)
Next K
DoEvents
Next i
Columns("A:IV").EntireColumn.AutoFit
End Sub
Took about 40 minutes on a Celery 1.1 GHZ with 300 or so megs-O-RAM, it got to row 11,000 or something and crashed, since VBA couldn't swallow the idea of a 5 digit year.