POSIX allows the '%Y' format in strftime to start with a '+' sign for years with more than 4 digits. test_time is not tolerant of that, which leads to failures like this with musl:

======================================================================
FAIL: test_large_year (test.test_time.TestStrftime4dyear)
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Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-alpine/build/Lib/test/test_time.py", line 683, in test_large_year
    return super().test_large_year()
  File "/buildbot/buildarea/3.x.ware-alpine/build/Lib/test/test_time.py", line 706, in test_large_year
    self.assertEqual(self.yearstr(12345), '12345')
AssertionError: '+12345' != '12345'
- +12345
? -
+ 12345