[tasks] Use the local timezone when comparing for the start time

Fix #7676

discord/ext/tasks/__init__.py

@@ -632,13 +632,14 @@ class Loop(Generic[LF]):
 
         if index is None:
             time = self._time[0]
-            tomorrow = now + datetime.timedelta(days=1)
+            tomorrow = now.astimezone(time.tzinfo) + datetime.timedelta(days=1)
             date = tomorrow.date()
         else:
-            date = now.date()
             time = self._time[index]
+            date = now.astimezone(time.tzinfo).date()
 
-        return resolve_datetime(datetime.datetime.combine(date, time, tzinfo=time.tzinfo or datetime.timezone.utc))
+        dt = datetime.datetime.combine(date, time, tzinfo=time.tzinfo)
+        return resolve_datetime(dt)
 
     def _start_time_relative_to(self, now: datetime.datetime) -> Optional[int]:
         # now kwarg should be a datetime.datetime representing the time "now"
@@ -651,10 +652,16 @@ class Loop(Generic[LF]):
         # For example, if given a list of times [0, 3, 18]
         # If it's 04:00 today then we know we have to wait until 18:00 today
         # If it's 19:00 today then we know we we have to wait until 00:00 tomorrow
-        date = now.date()
+        # Note that timezones need to be taken into consideration for this to work.
+        # If the timezone is set to UTC+9 and the now timezone is UTC
+        # A conversion needs to be done.
+        # i.e. 03:00 UTC+9 -> 18:00 UTC the previous day
         for idx, time in enumerate(self._time):
-            start_time = datetime.datetime.combine(date, time, tzinfo=time.tzinfo)
-            if start_time >= now:
+            # Convert the current time to the target timezone
+            # e.g. 18:00 UTC -> 03:00 UTC+9
+            # Then compare the time instances to see if they're the same
+            start = now.astimezone(time.tzinfo)
+            if time >= start.timetz():
                 return idx
         else:
             return None

tests/test_ext_tasks.py

@@ -102,7 +102,32 @@ def test_task_regression_issue7659():
 
     for before, expected_time in zip(minute_before, times):
         expected = datetime.datetime.combine(today, expected_time, tzinfo=jst)
-        assert loop._get_next_sleep_time(before) == expected
+        actual = loop._get_next_sleep_time(before)
+        assert actual == expected
+
+
+def test_task_regression_issue7676():
+    jst = datetime.timezone(datetime.timedelta(hours=9))
+
+    # 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00
+    times = [datetime.time(hour=h, tzinfo=jst) for h in range(0, 24, 3)]
+
+    @tasks.loop(time=times)
+    async def loop():
+        pass
+
+    # Create pseudo UTC times
+    now = utils.utcnow()
+    today = now.date()
+    times_before_in_utc = [
+        datetime.datetime.combine(today, time, tzinfo=jst).astimezone(datetime.timezone.utc) - datetime.timedelta(minutes=1)
+        for time in times
+    ]
+
+    for before, expected_time in zip(times_before_in_utc, times):
+        actual = loop._get_next_sleep_time(before)
+        actual_time = actual.timetz()
+        assert actual_time == expected_time
 
 
 @pytest.mark.skipif(sys.version_info < (3, 9), reason="zoneinfo requires 3.9")