diff --git a/bigquery/google/cloud/bigquery/_helpers.py b/bigquery/google/cloud/bigquery/_helpers.py
index dcea7b237a07..b72b55950b71 100644
--- a/bigquery/google/cloud/bigquery/_helpers.py
+++ b/bigquery/google/cloud/bigquery/_helpers.py
@@ -18,10 +18,10 @@
 from collections import OrderedDict
 import datetime
 
+from google.cloud._helpers import UTC
 from google.cloud._helpers import _date_from_iso8601_date
 from google.cloud._helpers import _datetime_from_microseconds
 from google.cloud._helpers import _datetime_to_rfc3339
-from google.cloud._helpers import _microseconds_from_datetime
 from google.cloud._helpers import _RFC3339_NO_FRACTION
 from google.cloud._helpers import _time_from_iso8601_time_naive
 from google.cloud._helpers import _to_bytes
@@ -150,7 +150,11 @@ def _bytes_to_json(value):
 def _timestamp_to_json(value):
     """Coerce 'value' to an JSON-compatible representation."""
     if isinstance(value, datetime.datetime):
-        value = _microseconds_from_datetime(value) / 1.0e6
+        if value.tzinfo not in (None, UTC):
+            # Convert to UTC and remove the time zone info.
+            value = value.replace(tzinfo=None) - value.utcoffset()
+        value = '%s %s+00:00' % (
+            value.date().isoformat(), value.time().isoformat())
     return value
 
 
diff --git a/bigquery/unit_tests/test__helpers.py b/bigquery/unit_tests/test__helpers.py
index 0e508aba2da0..affd52294fdd 100644
--- a/bigquery/unit_tests/test__helpers.py
+++ b/bigquery/unit_tests/test__helpers.py
@@ -546,13 +546,35 @@ def _call_fut(self, value):
     def test_w_float(self):
         self.assertEqual(self._call_fut(1.234567), 1.234567)
 
-    def test_w_datetime(self):
+    def test_w_string(self):
+        ZULU = '2016-12-20 15:58:27.339328+00:00'
+        self.assertEqual(self._call_fut(ZULU), ZULU)
+
+    def test_w_datetime_wo_zone(self):
+        import datetime
+        ZULU = '2016-12-20 15:58:27.339328+00:00'
+        when = datetime.datetime(2016, 12, 20, 15, 58, 27, 339328)
+        self.assertEqual(self._call_fut(when), ZULU)
+
+    def test_w_datetime_w_non_utc_zone(self):
+        import datetime
+
+        class _Zone(datetime.tzinfo):
+
+            def utcoffset(self, _):
+                return datetime.timedelta(minutes=-240)
+
+        ZULU = '2016-12-20 19:58:27.339328+00:00'
+        when = datetime.datetime(
+            2016, 12, 20, 15, 58, 27, 339328, tzinfo=_Zone())
+        self.assertEqual(self._call_fut(when), ZULU)
+
+    def test_w_datetime_w_utc_zone(self):
         import datetime
         from google.cloud._helpers import UTC
-        from google.cloud._helpers import _microseconds_from_datetime
-        when = datetime.datetime(2016, 12, 3, 14, 11, 27, tzinfo=UTC)
-        self.assertEqual(self._call_fut(when),
-                         _microseconds_from_datetime(when) / 1e6)
+        ZULU = '2016-12-20 15:58:27.339328+00:00'
+        when = datetime.datetime(2016, 12, 20, 15, 58, 27, 339328, tzinfo=UTC)
+        self.assertEqual(self._call_fut(when), ZULU)
 
 
 class Test_datetime_to_json(unittest.TestCase):
@@ -907,20 +929,20 @@ def test_to_api_repr_w_bool(self):
         self.assertEqual(param.to_api_repr(), EXPECTED)
 
     def test_to_api_repr_w_timestamp_datetime(self):
+        from google.cloud._helpers import UTC
         import datetime
-        from google.cloud._helpers import _microseconds_from_datetime
-        now = datetime.datetime.utcnow()
-        seconds = _microseconds_from_datetime(now) / 1.0e6
+        STAMP = '2016-12-20 15:58:27.339328+00:00'
+        when = datetime.datetime(2016, 12, 20, 15, 58, 27, 339328, tzinfo=UTC)
         EXPECTED = {
             'parameterType': {
                 'type': 'TIMESTAMP',
             },
             'parameterValue': {
-                'value': seconds,
+                'value': STAMP,
             },
         }
         klass = self._get_target_class()
-        param = klass.positional(type_='TIMESTAMP', value=now)
+        param = klass.positional(type_='TIMESTAMP', value=when)
         self.assertEqual(param.to_api_repr(), EXPECTED)
 
     def test_to_api_repr_w_timestamp_micros(self):
diff --git a/system_tests/bigquery.py b/system_tests/bigquery.py
index 3c266c760440..5b58ad2ee4da 100644
--- a/system_tests/bigquery.py
+++ b/system_tests/bigquery.py
@@ -482,9 +482,12 @@ def _job_done(instance):
     def test_sync_query_w_standard_sql_types(self):
         import datetime
         from google.cloud._helpers import UTC
+        from google.cloud.bigquery._helpers import ScalarQueryParameter
         naive = datetime.datetime(2016, 12, 5, 12, 41, 9)
         stamp = "%s %s" % (naive.date().isoformat(), naive.time().isoformat())
         zoned = naive.replace(tzinfo=UTC)
+        zoned_param = ScalarQueryParameter(
+            name='zoned', type_='TIMESTAMP', value=zoned)
         EXAMPLES = [
             {
                 'sql': 'SELECT 1',
@@ -553,9 +556,16 @@ def test_sync_query_w_standard_sql_types(self):
                 'sql': 'SELECT ARRAY(SELECT STRUCT([1, 2]))',
                 'expected': [{u'_field_1': [1, 2]}],
             },
+            {
+                'sql': 'SELECT @zoned',
+                'expected': zoned,
+                'query_parameters': [zoned_param],
+            },
         ]
         for example in EXAMPLES:
-            query = Config.CLIENT.run_sync_query(example['sql'])
+            query = Config.CLIENT.run_sync_query(
+                example['sql'],
+                query_parameters=example.get('query_parameters', ()))
             query.use_legacy_sql = False
             query.run()
             self.assertEqual(len(query.rows), 1)