The attach pic and info does not fully explain what your problem is. I realize we are all pressed for time, but it is only courteous to put the time into better explaining the problem rather than have the experts try to spend their time to figure out the missing pieces.
Having said that, dates are already sorted chronologically. No sorting needed. I believe your issue, which is obstructed by the dialog box in the screen image, is there is another dimension to the left of date on the rows shelf. Dimensions (including dates) can only be sorted WITHIN dimension groupings to the left.