There doesn't seem to be any way for Spotfire to take a date string in serial format (41397) and convert it into a working date. I know when the data table is being uploaded, it can be registered as a date and will be converted. For the purpose of my dashboard, I needed the column to stay in string format. What I ended up using was this formula to make the conversion: DateAdd("day",[Column],Date(1899,12,30)). The column portion contained the 5 digit serial format date and adds it to 30Dec1899 to give you the required date.