diff --git a/patchwork/parser.py b/patchwork/parser.py
index 729e19b4..15ac5a15 100644
--- a/patchwork/parser.py
+++ b/patchwork/parser.py
@@ -5,6 +5,7 @@
 
 import codecs
 import datetime
+from datetime import timezone
 from email.header import decode_header
 from email.header import make_header
 from email.utils import mktime_tz
@@ -468,7 +469,9 @@ def find_date(mail):
         return tz_utils.now()
 
     try:
-        d = datetime.datetime.utcfromtimestamp(mktime_tz(t))
+        d = datetime.datetime.fromtimestamp(
+            mktime_tz(t), tz=timezone.utc
+        ).replace(tzinfo=None)
     except (OverflowError, ValueError, OSError):
         # If you have a date like:
         # - Date: Wed, 4 Jun 207777777777777777777714 17:50:46 0
diff --git a/patchwork/views/utils.py b/patchwork/views/utils.py
index 91b2ef1b..cc8595d6 100644
--- a/patchwork/views/utils.py
+++ b/patchwork/views/utils.py
@@ -5,6 +5,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 import datetime
+from datetime import timezone
 from email.encoders import encode_7or8bit
 from email.header import Header
 from email.mime.nonmultipart import MIMENonMultipart
@@ -76,7 +77,9 @@ def _submission_to_mbox(submission):
     if is_patch and submission.diff:
         body += '\n' + submission.diff
 
-    delta = submission.date - datetime.datetime.utcfromtimestamp(0)
+    delta = submission.date - datetime.datetime.fromtimestamp(
+        0, tz=timezone.utc
+    ).replace(tzinfo=None)
     utc_timestamp = delta.seconds + delta.days * 24 * 3600
 
     mail = PatchMbox(body)