>>> from lunardate import LunarDate
        >>> LunarDate.from_solar_date(1976, 10, 1)
        LunarDate(1976, 8, 8, 1)
        >>> LunarDate(1976, 8, 8, 1).to_solar_date()
        datetime.date(1976, 10, 1)
        >>> LunarDate(1976, 8, 8, 1).year
        1976
        >>> LunarDate(1976, 8, 8, 1).month
        8
        >>> LunarDate(1976, 8, 8, 1).day
        8
        >>> LunarDate(1976, 8, 8, 1).is_leap_month
        True
        >>> today = LunarDate.today()
        >>> type(today).__name__
        'LunarDate'
        >>> # support '+' and '-' between datetime.date and datetime.timedelta
        >>> ld = LunarDate(1976,8,8)
        >>> sd = datetime.date(2008,1,1)
        >>> td = datetime.timedelta(days=10)
        >>> ld-ld
        datetime.timedelta(0)
        >>> ld-sd
        datetime.timedelta(-11444)
        >>> ld-td
        LunarDate(1976, 7, 27, 0)
        >>> sd-ld
        datetime.timedelta(11444)
        >>> ld+td
        LunarDate(1976, 8, 18, 0)
        >>> td+ld
        LunarDate(1976, 8, 18, 0)
        >>> ld2 = LunarDate.today()
        >>> ld < ld2
        True
        >>> ld <= ld2
        True
        >>> ld > ld2
        False
        >>> ld >= ld2
        False
        >>> ld == ld2
        False
        >>> ld != ld2
        True
        >>> ld == ld
        True
        >>> LunarDate.today() == LunarDate.today()
        True
        >>> LunarDate.leap_month_for_year(2023)
        2
        >>> LunarDate.leap_month_for_year(2022)
        None