Set time zone on login

Should be more reliable.

views/login.erb

@@ -4,7 +4,7 @@
   <p class="alert alert-warning mb-4"><%= @error %></p>
 <% end %>
 
-<form action="/login" method="post" class="mb-5">
+<form action="/login" name="login" method="post" class="mb-5">
   <div class="mb-3">
     <label for="email" class="form-label"><%= _("Email") %></label>
     <input type="text" name="email" class="form-control">
@@ -14,6 +14,11 @@
     <input type="password" name="password" class="form-control">
   </div>
   <button type="submit" class="btn btn-primary"><%= _("Login") %></button>
+  <input type="hidden" name="timezone" value="UTC">
 </form>
 <p><a href="/signup"><%= _("Create account") %></a></p>
 <p><a href="/reset"><%= _("Reset password") %></a></p>
+
+<script>
+document.login.timezone.value = Intl.DateTimeFormat().resolvedOptions().timeZone;
+</script>