I have a Mysql Table that is used for a log file on the that table there is a field called \'log_date\' And it stores the date in the following format( %Y-%m-%d %H:%i.%s ).O
You can try with that..
WHERE DATE_FORMAT(AUCTION_DATE, '%Y%m%d') >= DATE_FORMAT('2013/5/18', '%Y%m%d')
You can also get today date using now() function.