Dates and Grouping Error

Hi All,

So I am trying to group dates on a pivot but it keeps giving me an error stating that it cannot be done. The column that its pulling the info from has empty cells in it (not blank cells) meaning it still registers something in the cell even though its blank. I used to a formula to calculate the dates and told it to return an empty string "" if theres no date available, I tried to put in a dummy date in the string to account for all the blanks but it doesn't seem to work, any suggestions? thank you in advance.