Handle dates that fall within an hour of daylight saving time ending

dear_petition/petition/tests/test_utils.py

@@ -1,7 +1,4 @@
-import pytest
-from pytest_django.fixtures import settings
 import pytz
-from django.conf import settings
 from django.utils.timezone import make_aware, utc
 from datetime import datetime, date
 
@@ -75,6 +72,25 @@ def test_make_datetime_aware(settings):
     assert aware_dt == None
 
 
+def test_make_datetime_aware_ambiguous(settings):
+    """Aware Datetime should be returned assuming standard time in the case of ambiguity between standard time and
+    daylight saving time.
+    """
+    # Set the TIME_ZONE in the settings.
+    settings.TIME_ZONE = "America/New_York"
+
+    # Calling pu.make_datetime_aware() with a date/time that falls within the hour before or after daylight saving time
+    # ends returns a timezone-aware datetime referring to the moment from the naive_datetime_obj, in the appropriate
+    # time zone, assuming standard time.
+    naive_datetime_str = "2011-11-06T01:46:00"
+    expected_datetime_obj = make_aware(
+        datetime(year=2011, month=11, day=6, hour=1, minute=46, second=0),
+        timezone=pytz.timezone("America/New_York"),
+        is_dst=False
+    )
+    assert pu.make_datetime_aware(naive_datetime_str) == expected_datetime_obj
+
+
 def test_format_petition_date(settings):
     """Should return %m/%d/%Y date. If it is non-EST datetime, it will convert to EST first."""
 

dear_petition/petition/utils.py

@@ -48,9 +48,16 @@ def make_datetime_aware(dt_str):
     naive_datetime_obj = dateutil.parser.parse(dt_str)
 
     # b) Assign the timezone-naive datetime a timezone based on settings.TIME_ZONE
-    aware_datetime_obj = make_aware(
-        naive_datetime_obj, pytz.timezone(settings.TIME_ZONE)
-    )
+    tz = pytz.timezone(settings.TIME_ZONE)
+    try:
+        aware_datetime_obj = make_aware(naive_datetime_obj, tz)
+    except pytz.exceptions.AmbiguousTimeError:
+        # Ambiguity occurs when the date/time falls within the hour before or after daylight saving time ends. For
+        # example, if the date/time is November 6, 2011 01:46 AM, it is not known if the time is before or after the
+        # time change since that time occurs twice on that date. However, this level of granularity is not important in
+        # expungement, so default to standard time in case of ambiguity.
+        aware_datetime_obj = make_aware(naive_datetime_obj, tz, is_dst=False)
+
     # Return the timezone aware object.
     return aware_datetime_obj