when you give mysql a date, it
must be in year-month-day sequence
you could upload your dates into a varchar(10) column, alter the table to add a new column with DATE or DATETIME datatype, then update the table and use substring expressions to pull the pieces out of the varchar column to update the date column
Code:
update yourtable
set datecolumn
= concat_ws('/'
, substring(varcharcolumn
from locate('/',varcharcolumn,4)+1)
, left(varcharcolumn,locate('/',varcharcolumn,4)-1)
)