Take a look at Replace Field Contents. Using the calculation option, you can probably fix this issue. Replace Field Contents does the same modification calculation on all records of your found set. Since this is a major change that you can't undo, it's a good idea to make a back up copy of your file just before trying it out.
If this is a text field, I suggest defining a date field for this date and using Replace field contents to convert the date into a compatible format and move the data into a date field so that FileMaker can manipulate this value as a date rather than text.
Sorry for my ignorance but could you possibly be more specific. When I tried to do the change you described above I ended up inputting the same date for every record. What is the calculation I would use if the field I have is set up as a text and has all dates set up in the format I originall mentioned (YYYY-MM-DD)?
You use the calculation option in the Replace field contents so that it uses the current value of the text field to produce a date and enter it into the new date field.
Make a back up copy
Do a show all records to get all records into your found set.
Click/tab into the new date field
Select Replace Field Contents from the Records menu
Select the calculation option.
Enter a calculation similar to this:
Let ( d = YourTable::YourTextField ; Date ( Middle ( d ; 6 ; 2 ) ; Right ( d ; 2 ) ; Left ( d ; 4 ) )
Just substitute your table and field names in place of YourTable::YOurTextField.
I am assuming that all values for day and month are two digits long and that there are no spaces or other characters in the text field.
That was amazing thanks so much!!!