Chief developer Lukhnos has written on his blog on one particularity of Excel: the 1904 date system. The worksheets exported by TapExpense use the 1900 date system, which is the default used by Excel on Windows. If you use Excel for Mac and you need to copy-and-paste data from TapExpense-exported worksheets, you might want to read the entry on how Excel’s date systems might affect you, and how to correct the date differences caused the this curious design.