diff --git a/app/portal/__init__.py b/app/portal/__init__.py
index ad50ea8..115b6c8 100644
--- a/app/portal/__init__.py
+++ b/app/portal/__init__.py
@@ -16,16 +16,16 @@ portal = Blueprint("portal", __name__, template_folder="templates", static_folde
 
 
 @portal.app_template_filter("mirror_expiry")
-def calculate_mirror_expiry(s):
+def calculate_mirror_expiry(s: datetime) -> str:
     expiry = s + timedelta(days=3)
-    countdown = expiry - datetime.now(timezone.utc)
+    countdown = expiry - datetime.utcnow()
     if countdown.days == 0:
         return f"{countdown.seconds // 3600} hours"
     return f"{countdown.days} days"
 
 
 @portal.app_template_filter("format_datetime")
-def format_datetime(s):
+def format_datetime(s: datetime) -> str:
     if s is None:
         return "Unknown"
     return s.strftime("%a, %d %b %Y %H:%M:%S")