It sounds like there may not be any data in the new field. You can check this by typing "!empty12" into the simple search. This will look for resources without data in the date field. If the number of resources returned from the search is similar to the number of resources in the system it means the creation date data needs to be reimported.
Regardless of the results above you should verify that the recreated field exactly emulates the original with the information below (commas separate values):
12,date,Date,4,,80,1,0,0,creation_date,1,1,2#055,,,0,,DateTimeOriginal,0,0,,0,1,,0,0,"if ($value!=''){$value=nicedate($value,false);}",,,,,,
If it looks as though there is not data in the db for creation date, run "../pages/tools/update_exiftool_field.php?fieldrefs=12"
This will populate the field with exisiting data found in your current resource library.