/**
* 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;
}
