diff --git a/js/src/graphql/event.ts b/js/src/graphql/event.ts
index c0e1e9043..87e54ecb7 100644
--- a/js/src/graphql/event.ts
+++ b/js/src/graphql/event.ts
@@ -295,7 +295,7 @@ export const JOIN_EVENT = gql`
     $email: String
     $message: String
     $locale: String
-    $timezone: String
+    $timezone: Timezone
   ) {
     joinEvent(
       eventId: $eventId
diff --git a/js/src/graphql/user.ts b/js/src/graphql/user.ts
index e902488f0..33ef1bffa 100644
--- a/js/src/graphql/user.ts
+++ b/js/src/graphql/user.ts
@@ -151,7 +151,7 @@ export const LOGGED_USER_TIMEZONE = gql`
 
 export const SET_USER_SETTINGS = gql`
   mutation SetUserSettings(
-    $timezone: String
+    $timezone: Timezone
     $notificationOnDay: Boolean
     $notificationEachWeek: Boolean
     $notificationBeforeEvent: Boolean
diff --git a/js/src/views/Event/EditView.vue b/js/src/views/Event/EditView.vue
index 5fa261acc..19ca5b977 100644
--- a/js/src/views/Event/EditView.vue
+++ b/js/src/views/Event/EditView.vue
@@ -426,7 +426,9 @@
             >
               <option
                 v-for="timezone in groupTimezones"
-                :value="`${group}/${timezone}`"
+                :value="
+                  group === t('Other') ? timezone : `${group}/${timezone}`
+                "
                 :key="timezone"
               >
                 {{ sanitizeTimezone(timezone) }}
diff --git a/js/src/views/Settings/NotificationsView.vue b/js/src/views/Settings/NotificationsView.vue
index f1fa44eb7..d367469b7 100644
--- a/js/src/views/Settings/NotificationsView.vue
+++ b/js/src/views/Settings/NotificationsView.vue
@@ -73,7 +73,7 @@
             <tr v-for="subType in notificationType.subtypes" :key="subType.id">
               <td v-for="(method, key) in notificationMethods" :key="key">
                 <o-checkbox
-                  :value="notificationValues[subType.id][key].enabled"
+                  :modelValue="notificationValues[subType.id][key].enabled"
                   @update:modelValue="
                     (e: boolean) =>
                       updateNotificationValue({
@@ -645,7 +645,7 @@ const dialog = inject<Dialog>("dialog");
 
 const openRegenerateFeedTokensConfirmation = () => {
   dialog?.confirm({
-    type: "warning",
+    variant: "warning",
     title: t("Regenerate new links") as string,
     message: t(
       "You'll need to change the URLs where there were previously entered."
diff --git a/lib/graphql/schema.ex b/lib/graphql/schema.ex
index b74385db5..b635bc726 100644
--- a/lib/graphql/schema.ex
+++ b/lib/graphql/schema.ex
@@ -31,6 +31,7 @@ defmodule Mobilizon.GraphQL.Schema do
   import_types(Absinthe.Plug.Types)
   import_types(Custom.UUID)
   import_types(Custom.Point)
+  import_types(Custom.Timezone)
 
   import_types(Schema.ActivityType)
   import_types(Schema.UserType)
diff --git a/lib/graphql/schema/address.ex b/lib/graphql/schema/address.ex
index 0ca407f13..f1ec42a9f 100644
--- a/lib/graphql/schema/address.ex
+++ b/lib/graphql/schema/address.ex
@@ -22,7 +22,7 @@ defmodule Mobilizon.GraphQL.Schema.AddressType do
     field(:url, :string, description: "The address's URL")
     field(:id, :id, description: "The address's ID")
     field(:origin_id, :string, description: "The address's original ID from the provider")
-    field(:timezone, :string, description: "The (estimated) timezone of the location")
+    field(:timezone, :timezone, description: "The (estimated) timezone of the location")
     field(:picture_info, :picture_info, description: "A picture associated with the address")
   end
 
@@ -75,7 +75,7 @@ defmodule Mobilizon.GraphQL.Schema.AddressType do
     field(:url, :string, description: "The address's URL")
     field(:id, :id, description: "The address's ID")
     field(:origin_id, :string, description: "The address's original ID from the provider")
-    field(:timezone, :string, description: "The (estimated) timezone of the location")
+    field(:timezone, :timezone, description: "The (estimated) timezone of the location")
   end
 
   @desc """
diff --git a/lib/graphql/schema/config.ex b/lib/graphql/schema/config.ex
index 19c2fbec5..cc42f1b1a 100644
--- a/lib/graphql/schema/config.ex
+++ b/lib/graphql/schema/config.ex
@@ -43,7 +43,7 @@ defmodule Mobilizon.GraphQL.Schema.ConfigType do
 
     field(:upload_limits, :upload_limits, description: "The configuration for upload limits")
 
-    field(:timezones, list_of(:string), description: "The instance's available timezones")
+    field(:timezones, list_of(:timezone), description: "The instance's available timezones")
     field(:features, :features, description: "The instance's features")
     field(:restrictions, :restrictions, description: "The instance's restrictions")
     field(:version, :string, description: "The instance's version")
diff --git a/lib/graphql/schema/custom/timezone.ex b/lib/graphql/schema/custom/timezone.ex
new file mode 100644
index 000000000..cd20efc01
--- /dev/null
+++ b/lib/graphql/schema/custom/timezone.ex
@@ -0,0 +1,35 @@
+defmodule Mobilizon.GraphQL.Schema.Custom.Timezone do
+  @moduledoc """
+  The timezone scalar type allows timezone ID strings to be passed in and out.
+  """
+  use Absinthe.Schema.Notation
+  import Mobilizon.Web.Gettext, only: [dgettext: 3]
+
+  scalar :timezone, name: "Timezone" do
+    description("""
+    The `Timezone` scalar type represents a timezone identifier,
+    as registered in the IANA Time Zone Database.
+    """)
+
+    serialize(&encode/1)
+    parse(&decode/1)
+  end
+
+  @spec decode(Absinthe.Blueprint.Input.String.t()) :: {:ok, term} | :error
+  @spec decode(Absinthe.Blueprint.Input.Null.t()) :: {:ok, nil}
+  defp decode(%Absinthe.Blueprint.Input.String{value: value}) do
+    if Tzdata.zone_exists?(value),
+      do: {:ok, value},
+      else: {:error, dgettext("errors", "Timezone ID %{timezone} is invalid", timezone: value)}
+  end
+
+  defp decode(%Absinthe.Blueprint.Input.Null{}) do
+    {:ok, nil}
+  end
+
+  defp decode(_) do
+    :error
+  end
+
+  defp encode(value), do: value
+end
diff --git a/lib/graphql/schema/event.ex b/lib/graphql/schema/event.ex
index a44294ef6..544f565df 100644
--- a/lib/graphql/schema/event.ex
+++ b/lib/graphql/schema/event.ex
@@ -250,7 +250,7 @@ defmodule Mobilizon.GraphQL.Schema.EventType do
     field(:show_start_time, :boolean, description: "Show event start time")
     field(:show_end_time, :boolean, description: "Show event end time")
 
-    field(:timezone, :string, description: "The event's timezone")
+    field(:timezone, :timezone, description: "The event's timezone")
 
     field(:hide_organizer_when_group_event, :boolean,
       description:
@@ -303,7 +303,7 @@ defmodule Mobilizon.GraphQL.Schema.EventType do
     field(:show_start_time, :boolean, description: "Show event start time")
     field(:show_end_time, :boolean, description: "Show event end time")
 
-    field(:timezone, :string, description: "The event's timezone")
+    field(:timezone, :timezone, description: "The event's timezone")
 
     field(:hide_organizer_when_group_event, :boolean,
       description:
diff --git a/lib/graphql/schema/events/participant.ex b/lib/graphql/schema/events/participant.ex
index 6e61af84c..457e5b140 100644
--- a/lib/graphql/schema/events/participant.ex
+++ b/lib/graphql/schema/events/participant.ex
@@ -96,7 +96,7 @@ defmodule Mobilizon.GraphQL.Schema.Events.ParticipantType do
       arg(:email, :string, description: "The anonymous participant's email")
       arg(:message, :string, description: "The anonymous participant's message")
       arg(:locale, :string, description: "The anonymous participant's locale")
-      arg(:timezone, :string, description: "The anonymous participant's timezone")
+      arg(:timezone, :timezone, description: "The anonymous participant's timezone")
       middleware(Rajska.QueryAuthorization, permit: :all, rule: :"write:participation")
       resolve(&Participant.actor_join_event/3)
     end
diff --git a/lib/graphql/schema/user.ex b/lib/graphql/schema/user.ex
index 9fc640538..5588a414a 100644
--- a/lib/graphql/schema/user.ex
+++ b/lib/graphql/schema/user.ex
@@ -220,7 +220,7 @@ defmodule Mobilizon.GraphQL.Schema.UserType do
   """
   object :user_settings do
     meta(:authorize, :user)
-    field(:timezone, :string, description: "The timezone for this user")
+    field(:timezone, :timezone, description: "The timezone for this user")
 
     field(:notification_on_day, :boolean,
       description: "Whether this user will receive an email at the start of the day of an event."
@@ -450,7 +450,7 @@ defmodule Mobilizon.GraphQL.Schema.UserType do
 
     @desc "Set user settings"
     field :set_user_settings, :user_settings do
-      arg(:timezone, :string, description: "The timezone for this user")
+      arg(:timezone, :timezone, description: "The timezone for this user")
 
       arg(:notification_on_day, :boolean,
         description:
diff --git a/lib/graphql/schema/users/activity_setting.ex b/lib/graphql/schema/users/activity_setting.ex
index 4331fa1a1..5f58db04e 100644
--- a/lib/graphql/schema/users/activity_setting.ex
+++ b/lib/graphql/schema/users/activity_setting.ex
@@ -4,6 +4,7 @@ defmodule Mobilizon.GraphQL.Schema.Users.ActivitySetting do
   """
   use Absinthe.Schema.Notation
   alias Mobilizon.GraphQL.Resolvers.Users.ActivitySettings
+  alias Mobilizon.Users.ActivitySetting
 
   object :activity_setting do
     meta(:authorize, :user)
@@ -21,8 +22,9 @@ defmodule Mobilizon.GraphQL.Schema.Users.ActivitySetting do
 
       middleware(Rajska.QueryAuthorization,
         permit: :user,
-        scope: false,
-        rule: :"write:user:setting:activity"
+        scope: ActivitySetting,
+        rule: :"write:user:setting:activity",
+        args: %{key: :key}
       )
 
       resolve(&ActivitySettings.upsert_user_activity_setting/3)