Dates are stored in DB as such: \"2011-05-26 11:00:00\" in a datetime field. I\'d like to find all rows where the date is greater than the first of this month, ie: 2011-05-0
DATETIME fields can filtered just like integer fields, example:
DATETIME
SELECT * FROM `table` WHERE `date` > '2011-05-01 09:00:00'
In case you really want to convert to Unix timestamps, have a look at the UNIX_TIMESTAMP function.