The failure of the last-second addition to the timezone coversion test is
understood now: it can't work. Added comments explaining why (it's "the
usual"-- unrepresentable hours in local time --but in a slightly different
guise).
diff --git a/Lib/test/test_datetime.py b/Lib/test/test_datetime.py
index 3ef0772..4a7aa60 100644
--- a/Lib/test/test_datetime.py
+++ b/Lib/test/test_datetime.py
@@ -2591,7 +2591,6 @@
dston = datetimetz(2002, 4, 7, 2)
dstoff = datetimetz(2002, 10, 27, 2)
-
# Check a time that's inside DST.
def checkinside(self, dt, tz, utc, dston, dstoff):
self.assertEqual(dt.dst(), HOUR)
@@ -2691,9 +2690,18 @@
# hours" don't overlap.
self.convert_between_tz_and_utc(Eastern, Pacific)
self.convert_between_tz_and_utc(Pacific, Eastern)
- # XXX These fail!
- #self.convert_between_tz_and_utc(Eastern, Central)
- #self.convert_between_tz_and_utc(Central, Eastern)
+ # OTOH, these fail! Don't enable them. The difficulty is that
+ # the edge case tests assume that every hour is representable in
+ # the "utc" class. This is always true for a fixed-offset tzinfo
+ # class (lke utc_real and utc_fake), but not for Eastern or Central.
+ # For these adjacent DST-aware time zones, the range of time offsets
+ # tested ends up creating hours in the one that aren't representable
+ # in the other. For the same reason, we would see failures in the
+ # Eastern vs Pacific tests too if we added 3*HOUR to the list of
+ # offset deltas in convert_between_tz_and_utc().
+ #
+ # self.convert_between_tz_and_utc(Eastern, Central) # can't work
+ # self.convert_between_tz_and_utc(Central, Eastern) # can't work
def test_suite():