diff --git a/superset/utils/dates.py b/superset/utils/dates.py
index b2b422a1f09..b240bf5ab40 100644
--- a/superset/utils/dates.py
+++ b/superset/utils/dates.py
@@ -24,7 +24,7 @@ EPOCH = datetime(1970, 1, 1)
 def datetime_to_epoch(dttm: datetime) -> float:
     """Convert datetime to milliseconds to epoch"""
     if dttm.tzinfo:
-        dttm = dttm.replace(tzinfo=pytz.utc)
+        dttm = dttm.astimezone(pytz.utc)
         epoch_with_tz = pytz.utc.localize(EPOCH)
         return (dttm - epoch_with_tz).total_seconds() * 1000
     return (dttm - EPOCH).total_seconds() * 1000
diff --git a/tests/unit_tests/utils/json_tests.py b/tests/unit_tests/utils/json_tests.py
index 89c0a5a1657..957ce5e251a 100644
--- a/tests/unit_tests/utils/json_tests.py
+++ b/tests/unit_tests/utils/json_tests.py
@@ -24,6 +24,7 @@ from unittest.mock import MagicMock
 import numpy as np
 import pandas as pd
 import pytest
+import pytz
 
 from superset.utils import json
 from superset.utils.core import (
@@ -252,6 +253,11 @@ def test_json_int_dttm_ser():
     assert json.json_int_dttm_ser(datetime(1970, 1, 1)) == 0
     assert json.json_int_dttm_ser(date(1970, 1, 1)) == 0
     assert json.json_int_dttm_ser(dttm + timedelta(milliseconds=1)) == (ts + 1)
+
+    # Timezone-aware datetime should preserve the absolute instant.
+    # 2020-01-01 00:00:00+08:00 == 2019-12-31 16:00:00Z
+    dttm_tz = datetime(2020, 1, 1, tzinfo=pytz.FixedOffset(8 * 60))
+    assert json.json_int_dttm_ser(dttm_tz) == 1577808000000.0
     assert json.json_int_dttm_ser(np.int64(1)) == 1
 
     with pytest.raises(TypeError):