SQL – Change DATE from SQL

for DATETIME:

UPDATE table_name
SET date_col=DATE_FORMAT(date_col,'2013-%m-%d %T');

for DATE:

UPDATE table_name
SET date_col=DATE_FORMAT(date_col,'2013-%m-%d');

for CONCAT

UPDATE table_name SET field_name = 
concat('2011-01-12 ', time(field_name))

for +- INTERVAL

UPDATE table_name 
SET date_col= date_col + INTERVAL 5 DAY
WHERE ...

(you can use MONTH, YEAR, HOUR etc too)