- Fixed case where tzrange.utcoffset and tzrange.dst() might fail due

  to a date being used where a datetime was expected (reported and fixed
  by Lennart Regebro).
- Prevent tzstr from introducing daylight timings in strings that didn't
  specify them (reported by Lennart Regebro).
- Calls like gettz("GMT+3") and gettz("UTC-2") will now return the
  expected values, instead of the TZ variable behavior.

4 files changed, 56 insertions, 12 deletions

diff --git a/NEWS b/NEWS
index 6a80ca4..27fd1cc 100644
--- a/NEWS
+++ b/NEWS
@@ -1,10 +1,20 @@
 Version 1.4
 -----------
 
-- Fixed another precision problem on conversion of decimal seconds to
-  microseconds, as reported by Erik Brown.  Now they're gone for real,
-  since it's not using floating point arithmetic anymore.
+- Fixed another parser precision problem on conversion of decimal seconds
+  to microseconds, as reported by Erik Brown.  Now these issues are gone
+  for real since it's not using floating point arithmetic anymore.
 
+- Fixed case where tzrange.utcoffset and tzrange.dst() might fail due
+  to a date being used where a datetime was expected (reported and fixed
+  by Lennart Regebro).
+
+- Prevent tzstr from introducing daylight timings in strings that didn't
+  specify them (reported by Lennart Regebro).
+
+- Calls like gettz("GMT+3") and gettz("UTC-2") will now return the
+  expected values, instead of the TZ variable behavior.
+  
 
 
 Version 1.3
diff --git a/dateutil/parser.py b/dateutil/parser.py
index b1b7cc2..5d824e4 100644
--- a/dateutil/parser.py
+++ b/dateutil/parser.py
@@ -741,6 +741,8 @@ class _tzparser(object):
                     if (i < len_l and
                         (l[i] in ('+', '-') or l[i][0] in "0123456789")):
                         if l[i] in ('+', '-'):
+                            # Yes, that's right.  See the TZ variable
+                            # documentation.
                             signal = (1,-1)[l[i] == '+']
                             i += 1
                         else:
@@ -863,7 +865,7 @@ class _tzparser(object):
 
         except (IndexError, ValueError, AssertionError):
             return None
-
+        
         return res
 
 
diff --git a/dateutil/tz.py b/dateutil/tz.py
index 61fe2c1..0e28d6b 100644
--- a/dateutil/tz.py
+++ b/dateutil/tz.py
@@ -438,7 +438,7 @@ class tzfile(datetime.tzinfo):
 
         # The documentation says that utcoffset()-dst() must
         # be constant for every dt.
-        return self._find_ttinfo(dt, laststd=1).delta-tti.delta
+        return tti.delta-self._find_ttinfo(dt, laststd=1).delta
 
         # An alternative for that would be:
         #
@@ -492,12 +492,12 @@ class tzrange(datetime.tzinfo):
             self._dst_offset = self._std_offset+datetime.timedelta(hours=+1)
         else:
             self._dst_offset = ZERO
-        if start is None:
+        if dstabbr and start is None:
             self._start_delta = relativedelta.relativedelta(
                     hours=+2, month=4, day=1, weekday=relativedelta.SU(+1))
         else:
             self._start_delta = start
-        if end is None:
+        if dstabbr and end is None:
             self._end_delta = relativedelta.relativedelta(
                     hours=+1, month=10, day=31, weekday=relativedelta.SU(-1))
         else:
@@ -524,7 +524,7 @@ class tzrange(datetime.tzinfo):
     def _isdst(self, dt):
         if not self._start_delta:
             return False
-        year = datetime.date(dt.year,1,1)
+        year = datetime.datetime(dt.year,1,1)
         start = year+self._start_delta
         end = year+self._end_delta
         dt = dt.replace(tzinfo=None)
@@ -563,6 +563,11 @@ class tzstr(tzrange):
         if res is None:
             raise ValueError, "unknown string format"
 
+        # Here we break the compatibility with the TZ variable handling.
+        # GMT-3 actually *means* the timezone -3.
+        if res.stdabbr in ("GMT", "UTC"):
+            res.stdoffset *= -1
+
         # We must initialize it first, since _delta() needs
         # _std_offset and _dst_offset set. Use False in start/end
         # to avoid building it two times.
@@ -570,9 +575,13 @@ class tzstr(tzrange):
                          res.dstabbr, res.dstoffset,
                          start=False, end=False)
 
-        self._start_delta = self._delta(res.start)
-        if self._start_delta:
-            self._end_delta = self._delta(res.end, isend=1)
+        if not res.dstabbr:
+            self._start_delta = None
+            self._end_delta = None
+        else:
+            self._start_delta = self._delta(res.start)
+            if self._start_delta:
+                self._end_delta = self._delta(res.end, isend=1)
 
     def _delta(self, x, isend=0):
         kwargs = {}
diff --git a/test.py b/test.py
index c99efff..b7ad75e 100644
--- a/test.py
+++ b/test.py
@@ -3871,7 +3871,7 @@ END:VTIMEZONE
         tz = zoneinfo.gettz("EST5EDT")
         self.assertEqual(datetime(2003,4,6,1,59,tzinfo=tz).tzname(), "EST")
         self.assertEqual(datetime(2003,4,6,2,00,tzinfo=tz).tzname(), "EDT")
-        
+
     def testZoneInfoFileEnd1(self):
         tz = zoneinfo.gettz("EST5EDT")
         self.assertEqual(datetime(2003,10,26,0,59,tzinfo=tz).tzname(), "EDT")
@@ -3899,6 +3899,29 @@ END:VTIMEZONE
         tz = tzfile(StringIO(base64.decodestring(self.NEW_YORK)))
         self.assertEquals(datetime(2007,3,31,20,12).tzname(), None)
 
+    def testBrokenIsDstHandling(self):
+        # tzrange._isdst() was using a date() rather than a datetime().
+        # Issue reported by Lennart Regebro.
+        dt = datetime(2007,8,6,4,10, tzinfo=tzutc())
+        self.assertEquals(dt.astimezone(tz=gettz("GMT+2")),
+                          datetime(2007,8,6,6,10, tzinfo=tzstr("GMT+2")))
+
+    def testGMTHasNoDaylight(self):
+        # tzstr("GMT+2") improperly considered daylight saving time.
+        # Issue reported by Lennart Regebro.
+        dt = datetime(2007,8,6,4,10)
+        self.assertEquals(gettz("GMT+2").dst(dt), timedelta(0))
+
+    def testGMTOffset(self):
+        # GMT and UTC offsets have inverted signal when compared to the
+        # usual TZ variable handling.
+        dt = datetime(2007,8,6,4,10, tzinfo=tzutc())
+        self.assertEquals(dt.astimezone(tz=tzstr("GMT+2")),
+                          datetime(2007,8,6,6,10, tzinfo=tzstr("GMT+2")))
+        self.assertEquals(dt.astimezone(tz=gettz("UTC-2")),
+                          datetime(2007,8,6,2,10, tzinfo=tzstr("UTC-2")))
+
+
 if __name__ == "__main__":
 	unittest.main()