diff --git a/sc2reader/engine/plugins/gameheart.py b/sc2reader/engine/plugins/gameheart.py
index f2af2e82..c7994f4b 100644
--- a/sc2reader/engine/plugins/gameheart.py
+++ b/sc2reader/engine/plugins/gameheart.py
@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime, timezone
 from sc2reader.utils import Length, get_real_type
 from sc2reader.objects import Observer, Team
 from sc2reader.engine.events import PluginExit
@@ -65,8 +65,9 @@ def handleInitGame(self, event, replay):
         replay.real_length = Length(
             seconds=int(replay.game_length.seconds / GAME_SPEED_FACTOR[replay.speed])
         )
-        replay.start_time = datetime.utcfromtimestamp(
-            replay.unix_timestamp - replay.real_length.seconds
+        replay.start_time = datetime.fromtimestamp(
+            replay.unix_timestamp - replay.real_length.seconds,
+            timezone.utc
         )
 
     def fix_events(self, replay, start_frame):
diff --git a/sc2reader/resources.py b/sc2reader/resources.py
index 7bb3b9a9..855bb27f 100644
--- a/sc2reader/resources.py
+++ b/sc2reader/resources.py
@@ -1,5 +1,5 @@
 from collections import defaultdict, namedtuple
-from datetime import datetime
+from datetime import datetime, timezone
 import hashlib
 from xml.etree import ElementTree
 import zlib
@@ -411,7 +411,10 @@ def load_details(self):
 
         self.windows_timestamp = details["file_time"]
         self.unix_timestamp = utils.windows_to_unix(self.windows_timestamp)
-        self.end_time = datetime.utcfromtimestamp(self.unix_timestamp)
+        self.end_time = datetime.fromtimestamp(
+            self.unix_timestamp,
+            timezone.utc
+        )
 
         # The utc_adjustment is either the adjusted windows timestamp OR
         # the value required to get the adjusted timestamp. We know the upper
@@ -429,8 +432,9 @@ def load_details(self):
             seconds=self.length.seconds
             // GAME_SPEED_FACTOR[self.expansion].get(self.speed, 1.0)
         )
-        self.start_time = datetime.utcfromtimestamp(
-            self.unix_timestamp - self.real_length.seconds
+        self.start_time = datetime.fromtimestamp(
+            self.unix_timestamp - self.real_length.seconds,
+            timezone.utc
         )
         self.date = self.end_time  # backwards compatibility
 
@@ -1088,7 +1092,10 @@ def __init__(self, summary_file, filename=None, lang="enUS", **options):
         else:
             self.expansion = ""
 
-        self.end_time = datetime.utcfromtimestamp(self.parts[0][8])
+        self.end_time = datetime.fromtimestamp(
+            self.parts[0][8],
+            timezone.utc
+        )
         self.game_speed = LOBBY_PROPERTIES[0xBB8][1][self.parts[0][0][1].decode("utf8")]
         self.game_length = utils.Length(seconds=self.parts[0][7])
         self.real_length = utils.Length(
@@ -1096,8 +1103,9 @@ def __init__(self, summary_file, filename=None, lang="enUS", **options):
                 self.parts[0][7] / GAME_SPEED_FACTOR[self.expansion][self.game_speed]
             )
         )
-        self.start_time = datetime.utcfromtimestamp(
-            self.parts[0][8] - self.real_length.seconds
+        self.start_time = datetime.fromtimestamp(
+            self.parts[0][8] - self.real_length.seconds,
+            timezone.utc
         )
 
         self.load_map_info()