Return true if the value of the specified lhs object is less than the value of the specified rhs object, and false otherwise. A Datetime object a is less than a Datetime object b if a.date() < b.date(), or if a.date() == b.date() and the time portion of a is less than the time portion of b. The behavior is undefined unless 24 != lhs.hour() && 24 != rhs.hour().