Find conditions

I'm rails a newbie:

I have a form setup where users selects datetime, the datetime serves
the purpose of allowing the user to specify when the entry expires. In
efforts to filter entrys that have an earlier datetime than now I am

It is not completely clear from the above whether you are trying to
select records with an expiry date greater than now or earlier than

using the following:

def self.find_active
find(:all, :conditions => ['expiration > ?',])

It does not filter out the expiration inputs that are further in advance

What type of column (in the database) is expiration?