Easiest thing to do would probably to add a column to the table which is of type date, then write a little script which copies the value from your text column to the new column in proper date format.
Then sort by SQL whenever you want to.
Sth like
get all IDs and associated old dates from your db
UPDATE divx SET newDate='/ parse your old date in here /' WHERE divx.ID /or whatever you use as primary key/='/loop through all keys with this statement/
delete oldDate column
Shouldnt be too much trouble