The format is in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.
mysql> mysql> SELECT UTC_DATE(), UTC_DATE() + 0; +------------+----------------+ | UTC_DATE() | UTC_DATE() + 0 | +------------+----------------+ | 2007-07-23 | 20070723 | +------------+----------------+ 1 row in set (0.00 sec) mysql>