api/masto/marker: fix datetime format for updated_at

Ref: https://docs.joinmastodon.org/api/datetime-format/

Fixes: #1087

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased
 
+### Fixed
+- fix date-time format in `* /api/v1/markers` to strictly conform to Mastodon’s ISO 8061 subset
+
 ## 2026.03.1
 
 ### Fixed

lib/pleroma/web/mastodon_api/views/marker_view.ex

@@ -5,13 +5,15 @@
 defmodule Pleroma.Web.MastodonAPI.MarkerView do
   use Pleroma.Web, :view
 
+  alias Pleroma.Web.CommonAPI.Utils
+
   def render("markers.json", %{markers: markers}) do
     Map.new(markers, fn m ->
       {m.timeline,
        %{
          last_read_id: m.last_read_id,
          version: m.lock_version,
-         updated_at: NaiveDateTime.to_iso8601(m.updated_at),
+         updated_at: Utils.to_masto_date(m.updated_at),
          pleroma: %{
            unread_count: m.unread_count
          }

test/pleroma/web/mastodon_api/controllers/marker_controller_test.exs

@@ -13,7 +13,7 @@ defmodule Pleroma.Web.MastodonAPI.MarkerControllerTest do
       token = insert(:oauth_token, user: user, scopes: ["read:statuses"])
       insert_list(7, :notification, user: user, activity: insert(:note_activity))
 
-      {:ok, %{"notifications" => marker}} =
+      {:ok, %{"notifications" => _}} =
         Pleroma.Marker.upsert(
           user,
           %{"notifications" => %{"last_read_id" => "69420"}}
@@ -26,14 +26,14 @@ defmodule Pleroma.Web.MastodonAPI.MarkerControllerTest do
         |> get("/api/v1/markers?timeline[]=notifications")
         |> json_response_and_validate_schema(200)
 
-      assert response == %{
-               "notifications" => %{
-                 "last_read_id" => "69420",
-                 "updated_at" => NaiveDateTime.to_iso8601(marker.updated_at),
-                 "version" => 0,
-                 "pleroma" => %{"unread_count" => 7}
-               }
-             }
+      %{
+        "notifications" => %{
+          "last_read_id" => "69420",
+          "updated_at" => "" <> _,
+          "version" => 0,
+          "pleroma" => %{"unread_count" => 7}
+        }
+      } = response
     end
 
     test "gets markers with missed scopes", %{conn: conn} do
@@ -83,7 +83,7 @@ defmodule Pleroma.Web.MastodonAPI.MarkerControllerTest do
       user = insert(:user)
       token = insert(:oauth_token, user: user, scopes: ["write:statuses"])
 
-      {:ok, %{"notifications" => marker}} =
+      {:ok, %{"notifications" => _}} =
         Pleroma.Marker.upsert(
           user,
           %{"notifications" => %{"last_read_id" => "69477"}}
@@ -100,14 +100,14 @@ defmodule Pleroma.Web.MastodonAPI.MarkerControllerTest do
         })
         |> json_response_and_validate_schema(200)
 
-      assert response == %{
-               "notifications" => %{
-                 "last_read_id" => "69888",
-                 "updated_at" => NaiveDateTime.to_iso8601(marker.updated_at),
-                 "version" => 0,
-                 "pleroma" => %{"unread_count" => 0}
-               }
-             }
+      %{
+        "notifications" => %{
+          "last_read_id" => "69888",
+          "updated_at" => "" <> _,
+          "version" => 0,
+          "pleroma" => %{"unread_count" => 0}
+        }
+      } = response
     end
 
     test "creates a marker with missed scopes", %{conn: conn} do

test/pleroma/web/mastodon_api/views/marker_view_test.exs

@@ -7,6 +7,15 @@ defmodule Pleroma.Web.MastodonAPI.MarkerViewTest do
   alias Pleroma.Web.MastodonAPI.MarkerView
   import Pleroma.Factory
 
+  # Mastodon API only accepts a specific subset of ISO 8061
+  # (and we additionally truncate precision, eeventhough milliseconds are allowed)
+  defp expected_date(full_timestamp) do
+    full_timestamp
+    |> NaiveDateTime.truncate(:second)
+    |> NaiveDateTime.to_iso8601()
+    |> then(&(&1 <> ".000Z"))
+  end
+
   test "returns markers" do
     marker1 = insert(:marker, timeline: "notifications", last_read_id: "17", unread_count: 5)
     marker2 = insert(:marker, timeline: "home", last_read_id: "42")
@@ -14,13 +23,13 @@ defmodule Pleroma.Web.MastodonAPI.MarkerViewTest do
     assert MarkerView.render("markers.json", %{markers: [marker1, marker2]}) == %{
              "home" => %{
                last_read_id: "42",
-               updated_at: NaiveDateTime.to_iso8601(marker2.updated_at),
+               updated_at: expected_date(marker2.updated_at),
                version: 0,
                pleroma: %{unread_count: 0}
              },
              "notifications" => %{
                last_read_id: "17",
-               updated_at: NaiveDateTime.to_iso8601(marker1.updated_at),
+               updated_at: expected_date(marker1.updated_at),
                version: 0,
                pleroma: %{unread_count: 5}
              }