Hi, I think Excel may have automatically formatted the cells when you opened the .tsv file and changed the value of them. If you have a look at the file in a text editor, it should show the correct dates. A similar thing happened to me when I opened the .tsv file in Excel, it would automatically change dates from formats like 2/05/13 to 2/05/2013, so I didn't realise that some years were given as 2 digits or 4 digits. I hope this helps :)