def day_of_year(self):
        """
        Returns the day of the year (1-366).

        :rtype: int
        """
        k = 1 if self.is_leap_year() else 2

        return (275 * self.month) // 9 - k * ((self.month + 9) // 12) + self.day - 30
Returns the day of the year (1-366).

        :rtype: int