/** * Returns the month of a date as a number between 1 and 12. * * The argument can be any expression as long as it resolves to a date. * * @see http://docs.mongodb.org/manual/reference/operator/aggregation/month/ * @see Expr::month * @param mixed|Expr $expression * @return self */ public function month($expression) { $this->expr->month($expression); return $this; }