excel date to unix timestamp
'VBA functions to convert between Excel and Unix date-times.
'These work on Windows and optionally the Mac:
Function UnixDateTime#(ExcelDateTime As Date, Optional Mac As Boolean)
Dim OSOffset: OSOffset = IIf(Mac, 24107, 25569)
UnixDateTime = (ExcelDateTime - OSOffset) * 86400
End Function
Function ExcelDateTime(UnixDateTime#, Optional Mac As Boolean) As Date
Dim OSOffset: OSOffset = IIf(Mac, 24107, 25569)
ExcelDateTime = (UnixDateTime / 86400) + OSOffset
End Function