Fix overflow error on 32bit systems

This fixes #87.

src/croniter/__init__.py

@@ -2,6 +2,7 @@
 from __future__ import absolute_import
 from .croniter import (
     croniter,
+    OVERFLOW32B_MODE,
     datetime_to_timestamp,
     croniter_range,
     CroniterBadTypeRangeError,  # noqa

src/croniter/croniter.py

@@ -21,6 +21,14 @@
 # python2, just test that it's well installed
 import pytz  # noqa
 
+EPOCH = datetime.datetime.fromtimestamp(0)
+try:
+    # https://github.com/python/cpython/issues/101069 detection
+    datetime.datetime.fromtimestamp(3999999999)
+    OVERFLOW32B_MODE = False
+except OverflowError:
+    OVERFLOW32B_MODE = True
+
 try:
     from collections import OrderedDict
 except ImportError:
@@ -274,7 +282,12 @@ def _timestamp_to_datetime(self, timestamp):
         """
         Converts a UNIX timestamp `timestamp` into a `datetime` object.
         """
-        result = datetime.datetime.fromtimestamp(timestamp, tz=tzutc()).replace(tzinfo=None)
+        if OVERFLOW32B_MODE:
+            # degraded mode to workaround Y2038
+            # see https://github.com/python/cpython/issues/101069
+            result = EPOCH + datetime.timedelta(seconds=timestamp)
+        else:
+            result = datetime.datetime.fromtimestamp(timestamp, tz=tzutc()).replace(tzinfo=None)
         if self.tzinfo:
             result = result.replace(tzinfo=tzutc()).astimezone(self.tzinfo)
 

src/croniter/tests/test_croniter.py

@@ -8,7 +8,7 @@
 import pytz
 from croniter.croniter import VALID_LEN_EXPRESSION
 from croniter import (croniter, CroniterBadDateError, CroniterBadCronError, datetime_to_timestamp,
-                      CroniterNotAlphaError, CroniterUnsupportedSyntaxError)
+                      CroniterNotAlphaError, CroniterUnsupportedSyntaxError, OVERFLOW32B_MODE)
 from croniter.tests import base
 import dateutil.tz
 
@@ -1962,6 +1962,14 @@ def test_get_next_update_current(self):
         self.assertEqual(uretp, uretap)
         self.assertEqual(uretn, uretan)
 
+    def test_issue_2038y(self):
+        base = datetime(2040, 1, 1, 0, 0)
+        itr = croniter('* * * * *', base)
+        try:
+            itr.get_next()
+        except OverflowError:
+            raise Exception("overflow not fixed!")
+
 
 if __name__ == '__main__':
     unittest.main()