inform users about start time if start time is in the future

frontend.py

@@ -1,7 +1,7 @@
 import random
 import socket
 from collections import defaultdict
-from datetime import datetime
+from datetime import datetime, timezone
 from secrets import token_hex
 from typing import Iterable
 
@@ -132,6 +132,20 @@ def before_request():
     g.avatar = session.get("gh_avatar")
 
 
+@app.context_processor
+def start_time_alert():
+    # if g.user is set, the user was successfully logged in (see above)
+    if g.user:
+        return {"start_time": None}
+
+    start_time = datetime.fromtimestamp(CONFIG["TIME_MIN"], timezone.utc)
+
+    if start_time < datetime.now(timezone.utc):
+        return {"start_time": None}
+
+    return {"start_time": start_time.strftime("%F %T")}
+
+
 @app.route("/github-callback")
 @github.authorized_handler
 def authorized(access_token):

templates/layout.jinja

@@ -45,6 +45,12 @@
     </nav>
     <div class="container" id='main'>
       <busy-indicator></busy-indicator>
+      {% if start_time %}
+        <div class="alert alert-info" role="alert">
+          <h2>Submissions are not yet open</h2>
+          <p>You will be able to submit content starting <span style="font-weight: bolder;">{{ start_time }} UTC</span></p>
+        </div>
+      {% endif %}
       {% block body %}
       {% endblock %}
       <hr/>