formating dates..

looks like your default system date format is not Y-M-D . I've had problems when the system date format is different from the date format in a col. so you could change the default date format as y-m-d.
alternatively, save the spreadsheet as text and open it in excel again, this time select the date column and specify the format as y-m-d.

Your dates are most likely text values. You don't
need a macro to convert them. Simply do the following:

1. Select the cells containing the text representation
of date values.
2. Choose the Data | Text to Columns... menu command.
3. At Step 1 of 3 press [ Next> ].
4. At Step 2 of 3 press [ Next> ].
5. At Step 3 of 3 choose the "Date" column format
radio button, select "MDY" from the date drop down
list, and press [ Finish ].

Here is a strange fix for you on these dates, and to make this work, you could probably just record a macro, but I found that just double-click the cell with the formatted date 1999-12-14, exit the cell, and it corrects the date to the format of 12-14-1999. I know if sounds flaky, but it accomplishes the same thing as going through and using the "text to columns" steps. I am just assuming that these dates were copied and pasted into excel, that is the only common variable I have experienced when I have encountered this problem.