alarms: handle missing last update

app/portal/__init__.py

@@ -20,6 +20,13 @@ def calculate_mirror_expiry(s):
     return f"{countdown.days} days"
 
 
+@portal.app_template_filter("format_datetime")
+def format_datetime(s):
+    if s is None:
+        return "Unknown"
+    return s.strftime("%a, %d %b %Y %H:%M:%S")
+
+
 @portal.route("/")
 def portal_home():
     return render_template("home.html.j2", section="home")