سير العمل البرمجي · إزاحة الشهر مع ضبط اليوم

from calendar import monthrange
from datetime import date

def add_months(day, delta):
    if type(day) is not date or type(delta) is not int:
        raise ValueError("month.input")
    year, month0 = divmod(day.year * 12 + day.month - 1 + delta, 12)
    if not 1 <= year <= 9999:
        raise ValueError("month.year")
    last = monthrange(year, month0 + 1)[1]
    return date(year, month0 + 1, min(day.day, last))