MySQL DATE TIME QUERY

SELECT UNIX_TIMESTAMP(YEAR(NOW()).'-'.MONTH(NOW()).'-'.DAY(NOW()))

SELECT UNIX_TIMESTAMP('2012-05-23');

// MONTH level
SELECT UNIX_TIMESTAMP(CONCAT(YEAR(NOW()),'-',MONTH(NOW()),'-01'));

// DAY level
SELECT UNIX_TIMESTAMP(CONCAT(YEAR(NOW()),'-',MONTH(NOW()),'-',DAY(NOW())));

// HOUR level
SELECT UNIX_TIMESTAMP(CONCAT(YEAR(NOW()),'-',MONTH(NOW()),'-',DAY(NOW()),' ',HOUR(NOW()),':00:00'));