finding yesterday and tomorrrow without using date.time module

[scidam]

I think, it would be better to create class that describes dates.

class Date:

    feb_max_length = 29
    allowed_month_lengths = {1: 31,
                             2: feb_max_length - 1,
                             3: 31,
                             4: 30,
                             5: 31,
                             6: 30,
                             7: 31,
                             8: 31,
                             9: 30,
                             10: 31,
                             11: 30,
                             12: 31
                             }
              
    def __init__(self, day, month, year):
        self.day = day
        self.month = month
        self.year = year
        self._validate()
        

    def _validate(self):

        if not(isinstance(self.year, int) and isinstance(self.month, int) and isinstance(self.day, int)):
            raise Exception("Error: year, month, day should be integers.")

        if not(1 <= self.month <= 12):
            raise Exception("Error: month should be in [1, 12], your value is {}.".format(self.month))

        if not (1 <= self.day <= self.month_length):
            raise Exception("Error: day number ({}) should be less or equal {}.".format(self.day, self.month_length))
        
       
    def __str__(self):
        return 'Date: {}.{}.{}'.format(self.day, self.month, self.year)
        
    def __repr__(self):
        return self.__str__()

    @property
    def is_leap_year(self):
        return self.year % 4 == 0 and (self.year % 100 != 0 or self.year % 400 == 0)
    
    @property
    def month_length(self):
        _ = self.allowed_month_lengths.get(self.month, None)
        return _ if not self.is_leap_year else (_ + 1 if self.month == 2 else _)
    
    @property
    def day_after(self):
        """Returns date = 1 day +  current date
        """

        if 1 <= self.day < self.month_length:
            return Date(self.day + 1, self.month, self.year)

        if self.day == self.month_length and self.month == 12:
            return Date(1, 1, self.year + 1)

        elif self.day == self.month_length and self.month < 12:
            return Date(1, self.month + 1, self.year)
    
    @property
    def day_before(self):
        raise NotImplementedError
        

d = Date(28, 2, 2019)
print("Current date:", d)
print("Next day: ", d.day_after)
print("Two days after:", d.day_after.day_after)