....
&&
(
    s.Created_at.Value.Day >= dateStart.Day && s.Created_at.Value.Day <= dateEnd.Day &&
    s.Created_at.Value.Month >= dateStart.Month && s.Created_at.Value.Month <= dateEnd.Month &&
    s.Created_at.Value.Year >= dateStart.Year && s.Created_at.Value.Year <= dateEnd.Year
)).count();