diff --git a/src/betamax/adapter.py b/src/betamax/adapter.py
index 8e8a0d2..2b2e5cb 100644
--- a/src/betamax/adapter.py
+++ b/src/betamax/adapter.py
@@ -9,7 +9,7 @@
 
 from . import cassette
 from .exceptions import BetamaxError
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from requests.adapters import BaseAdapter, HTTPAdapter
 
 _SENTINEL = object()
@@ -102,7 +102,7 @@ def load_cassette(self, cassette_name, serialize, options):
         if self.options.get('re_record_interval'):
             re_record_interval = timedelta(self.options['re_record_interval'])
 
-        now = datetime.utcnow()
+        now = datetime.now(timezone.utc).replace(tzinfo=None)
         if re_record_interval < (now - self.cassette.earliest_recorded_date):
             self.cassette.clear()
 
diff --git a/src/betamax/util.py b/src/betamax/util.py
index 3090acc..5355294 100644
--- a/src/betamax/util.py
+++ b/src/betamax/util.py
@@ -1,5 +1,5 @@
 from .mock_response import MockHTTPResponse
-from datetime import datetime
+from datetime import datetime, timezone
 from requests.models import PreparedRequest, Response
 from requests.packages.urllib3 import HTTPResponse
 from requests.structures import CaseInsensitiveDict
@@ -163,7 +163,7 @@ def add_urllib3_response(serialized, response, headers):
 
 
 def timestamp():
-    stamp = datetime.utcnow().isoformat()
+    stamp = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%S")
     try:
         i = stamp.rindex('.')
     except ValueError: