>>> import calendar

>>> calendar.month(2024, -1)
Traceback (most recent call last):
  File "<python-input-12>", line 1, in <module>
    calendar.month(2024, -1)
    ~~~~~~~~~~~~~~^^^^^^^^^^
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 395, in formatmonth
    for week in self.monthdays2calendar(theyear, themonth):
                ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 284, in monthdays2calendar
    days = list(self.itermonthdays2(year, month))
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 240, in itermonthdays2
    for i, d in enumerate(self.itermonthdays(year, month), self.firstweekday):
                ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 228, in itermonthdays
    day1, ndays = monthrange(year, month)
                  ~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 165, in monthrange
    raise IllegalMonthError(month)
calendar.IllegalMonthError: bad month number -1; must be 1-12

>>> calendar.month(2024, 13)
Traceback (most recent call last):
  File "<python-input-13>", line 1, in <module>
    calendar.month(2024, 13)
    ~~~~~~~~~~~~~~^^^^^^^^^^
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 390, in formatmonth
    s = self.formatmonthname(theyear, themonth, 7 * (w + 1) - 1)
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 373, in formatmonthname
    s = month_name[themonth]
        ~~~~~~~~~~^^^^^^^^^^
  File "/Users/gugu/Code/cpython/Lib/calendar.py", line 103, in __getitem__
    funcs = self._months[i]
            ~~~~~~~~~~~~^^^
IndexError: list index out of range