CONVERT_TZ() converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value.
CONVERT_TZ() returns NULL if the arguments are invalid.
mysql>
mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','GMT','MET');
+-----------------------------------------------+
| CONVERT_TZ('2004-01-01 12:00:00','GMT','MET') |
+-----------------------------------------------+
| NULL |
+-----------------------------------------------+
1 row in set (0.02 sec)