@classmethod
def _month_length(cls, year, month):
    """Months start with Nissan (Nissan is 1 and Tishrei is 7)"""
    if month in [1, 3, 5, 7, 11]:
        return 30
    elif month in [2, 4, 6, 10, 13]:
        return 29
    elif month == 12:
        return 30 if cls._is_leap(year) else 29
    elif month == 8:
        return 30 if cls._long_cheshvan(year) else 29
    elif month == 9:
        return 29 if cls._short_kislev(year) else 30
