diff --git a/nats/js/api.py b/nats/js/api.py
index d3aae15f..cf994f49 100644
--- a/nats/js/api.py
+++ b/nats/js/api.py
@@ -96,25 +96,32 @@ def _convert_rfc3339(resp: Dict[str, Any], field: str) -> None:
         val = resp.get(field, None)
         if val is None:
             return None
-        # Handle Zulu
-        offset = "+00:00"
+        # Handle Zulu (UTC)
+        # Until python < 3.11, fromisoformat() do not accept "Z" as a valid
+        # timezone. See: https://github.com/python/cpython/issues/80010
         if val.endswith("Z"):
+            offset = "+00:00"
             raw_date = val[:-1]
-        # There MUST be an offset if not Zulu
+        # There MUST be an offset if not Zulu.
+        # Until python3.11, fromisoformat() only accepts 3 or 6 decimal places for
+        # fractional seconds. See: https://github.com/python/cpython/issues/95221
+        # In order to pad missing microseconds, we need to temporary remove the offset.
+        # Offset has a fixed sized of 5 characters.
         else:
             offset = val[-6:]
             raw_date = val[:-6]
-        # Padd missing milliseconds
-        if "." not in raw_date:
-            raw_date += ".000000"
-        else:
+        # Pad missing microseconds by adding "0" until length is 26.
+        # 26 is the length of a valid RFC3339 string with microseconds precision.
+        # Since python datetimes do not support more than 6 decimal places
+        # we need to truncate the string if it has more than 6 decimal places
+        if "." in raw_date:
             raw_date = raw_date[:26]
             length = len(raw_date)
             if length < 26:
                 raw_date += "0" * (26 - length)
-        # Add offset    
+        # Add offset back
         raw_date = raw_date + offset
-        # Parse into datetime using fromisoformat
+        # Parse string into datetime using fromisoformat
         resp[field] = datetime.datetime.fromisoformat(raw_date).astimezone(
             datetime.timezone.utc
         )
diff --git a/tests/test_js.py b/tests/test_js.py
index 758355ca..7ce88ccf 100644
--- a/tests/test_js.py
+++ b/tests/test_js.py
@@ -1400,7 +1400,9 @@ async def test_consumer_with_opt_start_time_date_only(self):
             deliver_policy=api.DeliverPolicy.BY_START_TIME,
         )
         assert isinstance(con.created, datetime.datetime)
-        assert con.config.opt_start_time == datetime.datetime(1970, 1, 1, tzinfo=datetime.timezone.utc)
+        assert con.config.opt_start_time == datetime.datetime(
+            1970, 1, 1, tzinfo=datetime.timezone.utc
+        )
         await nc.close()
 
     @async_test
@@ -1415,7 +1417,9 @@ async def test_consumer_with_opt_start_time_timestamp(self):
             deliver_policy=api.DeliverPolicy.BY_START_TIME,
         )
         assert isinstance(con.created, datetime.datetime)
-        assert con.config.opt_start_time == datetime.datetime(1970, 1, 1, 1, 1, 1, tzinfo=datetime.timezone.utc)
+        assert con.config.opt_start_time == datetime.datetime(
+            1970, 1, 1, 1, 1, 1, tzinfo=datetime.timezone.utc
+        )
         await nc.close()
 
     @async_test
@@ -1426,12 +1430,21 @@ async def test_consumer_with_opt_start_time_microseconds(self):
         await jsm.add_stream(name="ctests", subjects=["a", "b", "c.>"])
         con = await jsm.add_consumer(
             "ctests",
-            opt_start_time=datetime.datetime(1970, 1, 1, 1, 1, 1, microsecond=123456),
+            opt_start_time=datetime.datetime(
+                1970, 1, 1, 1, 1, 1, microsecond=123456
+            ),
             deliver_policy=api.DeliverPolicy.BY_START_TIME,
         )
         assert isinstance(con.created, datetime.datetime)
         assert con.config.opt_start_time == datetime.datetime(
-            1970, 1, 1, 1, 1, 1, microsecond=123456, tzinfo=datetime.timezone.utc
+            1970,
+            1,
+            1,
+            1,
+            1,
+            1,
+            microsecond=123456,
+            tzinfo=datetime.timezone.utc
         )
         await nc.close()
 
@@ -1443,11 +1456,15 @@ async def test_consumer_with_opt_start_time_date_tz(self):
         await jsm.add_stream(name="ctests", subjects=["a", "b", "c.>"])
         con = await jsm.add_consumer(
             "ctests",
-            opt_start_time=datetime.datetime(1970, 1, 1, tzinfo=pytz.timezone("Europe/Paris")),
+            opt_start_time=datetime.datetime(
+                1970, 1, 1, tzinfo=pytz.timezone("Europe/Paris")
+            ),
             deliver_policy=api.DeliverPolicy.BY_START_TIME,
         )
         assert isinstance(con.created, datetime.datetime)
-        assert con.config.opt_start_time == datetime.datetime(1970, 1, 1, tzinfo=pytz.timezone("Europe/Paris"))
+        assert con.config.opt_start_time == datetime.datetime(
+            1970, 1, 1, tzinfo=pytz.timezone("Europe/Paris")
+        )
         await nc.close()
 
     @async_test
@@ -1458,11 +1475,15 @@ async def test_consumer_with_opt_start_time_timestamp_tz(self):
         await jsm.add_stream(name="ctests", subjects=["a", "b", "c.>"])
         con = await jsm.add_consumer(
             "ctests",
-            opt_start_time=datetime.datetime(1970, 1, 1, 1, 1, 1, tzinfo=pytz.timezone("Europe/Paris")),
+            opt_start_time=datetime.datetime(
+                1970, 1, 1, 1, 1, 1, tzinfo=pytz.timezone("Europe/Paris")
+            ),
             deliver_policy=api.DeliverPolicy.BY_START_TIME,
         )
         assert isinstance(con.created, datetime.datetime)
-        assert con.config.opt_start_time == datetime.datetime(1970, 1, 1, 1, 1, 1, tzinfo=pytz.timezone("Europe/Paris"))
+        assert con.config.opt_start_time == datetime.datetime(
+            1970, 1, 1, 1, 1, 1, tzinfo=pytz.timezone("Europe/Paris")
+        )
         await nc.close()
 
     @async_test
@@ -1474,30 +1495,44 @@ async def test_consumer_with_opt_start_time_microseconds_tz(self):
         con = await jsm.add_consumer(
             "ctests",
             opt_start_time=datetime.datetime(
-                1970, 1, 1, 1, 1, 1, microsecond=123456, tzinfo=pytz.timezone("Europe/Paris")
+                1970,
+                1,
+                1,
+                1,
+                1,
+                1,
+                microsecond=123456,
+                tzinfo=pytz.timezone("Europe/Paris")
             ),
             deliver_policy=api.DeliverPolicy.BY_START_TIME,
         )
         assert isinstance(con.created, datetime.datetime)
         assert con.config.opt_start_time == datetime.datetime(
-            1970, 1, 1, 1, 1, 1, microsecond=123456, tzinfo=pytz.timezone("Europe/Paris")
+            1970,
+            1,
+            1,
+            1,
+            1,
+            1,
+            microsecond=123456,
+            tzinfo=pytz.timezone("Europe/Paris")
         )
         await nc.close()
 
     def test_parser_consumer_info_with_created_timestamp(self):
         for created in [
-            "1970-01-01T01:02:03Z",
-            "1970-01-01T02:02:03+01:00",
-            "1970-01-01T01:02:03.0Z",
-            "1970-01-01T01:02:03.00Z",
-            "1970-01-01T01:02:03.000Z",
-            "1970-01-01T01:02:03.0000Z",
-            "1970-01-01T01:02:03.00000Z",
-            "1970-01-01T01:02:03.000000Z",
-            "1970-01-01T01:02:03.0000000Z",
-            "1970-01-01T01:02:03.00000000Z",
-            "1970-01-01T01:02:03.000000000Z",
-            "1970-01-01T02:02:03.000000000Z+01:00",
+                "1970-01-01T01:02:03Z",
+                "1970-01-01T02:02:03+01:00",
+                "1970-01-01T01:02:03.0Z",
+                "1970-01-01T01:02:03.00Z",
+                "1970-01-01T01:02:03.000Z",
+                "1970-01-01T01:02:03.0000Z",
+                "1970-01-01T01:02:03.00000Z",
+                "1970-01-01T01:02:03.000000Z",
+                "1970-01-01T01:02:03.0000000Z",
+                "1970-01-01T01:02:03.00000000Z",
+                "1970-01-01T01:02:03.000000000Z",
+                "1970-01-01T02:02:03.000000000Z+01:00",
         ]:
             info = api.ConsumerInfo.from_response({
                 "name": "test",
@@ -1510,21 +1545,21 @@ def test_parser_consumer_info_with_created_timestamp(self):
                 1970, 1, 1, 1, 2, 3, tzinfo=datetime.timezone.utc
             )
         for created in [
-            "1970-01-01T01:02:03.4Z",
-            "1970-01-01T01:02:03.4+00:00",
-            "1970-01-01T01:02:03.40Z",
-            "1970-01-01T02:02:03.40+01:00",
-            "1970-01-01T01:02:03.400Z",
-            "1970-01-01T04:02:03.400+03:00",
-            "1970-01-01T01:02:03.4000Z",
-            "1970-01-01T07:22:03.4000+06:20",
-            "1970-01-01T01:02:03.40000Z",
-            "1970-01-01T00:02:03.400000-01:00",
-            "1970-01-01T01:02:03.400000Z",
-            "1970-01-01T01:02:03.4000000Z",
-            "1970-01-01T01:02:03.40000000Z",
-            "1970-01-01T01:02:03.400000000Z",
-            "1970-01-01T02:02:03.400000000Z+01:00",
+                "1970-01-01T01:02:03.4Z",
+                "1970-01-01T01:02:03.4+00:00",
+                "1970-01-01T01:02:03.40Z",
+                "1970-01-01T02:02:03.40+01:00",
+                "1970-01-01T01:02:03.400Z",
+                "1970-01-01T04:02:03.400+03:00",
+                "1970-01-01T01:02:03.4000Z",
+                "1970-01-01T07:22:03.4000+06:20",
+                "1970-01-01T01:02:03.40000Z",
+                "1970-01-01T00:02:03.400000-01:00",
+                "1970-01-01T01:02:03.400000Z",
+                "1970-01-01T01:02:03.4000000Z",
+                "1970-01-01T01:02:03.40000000Z",
+                "1970-01-01T01:02:03.400000000Z",
+                "1970-01-01T02:02:03.400000000Z+01:00",
         ]:
             info = api.ConsumerInfo.from_response({
                 "name": "test",