diff --git a/lib/change_builders/full_diff/helpers.ex b/lib/change_builders/full_diff/helpers.ex
index 87c1454..00135e5 100644
--- a/lib/change_builders/full_diff/helpers.ex
+++ b/lib/change_builders/full_diff/helpers.ex
@@ -98,13 +98,19 @@ defmodule AshPaperTrail.ChangeBuilders.FullDiff.Helpers do
   def unique_id(%Ash.Union{}, dumped_value), do: dumped_value
   def unique_id(nil, _dumped_value), do: nil
 
-  def unique_id(%{__struct__: resource}, dump_value) do
-    case Ash.Resource.Info.primary_key(resource) do
-      [] ->
-        nil
-
-      primary_keys ->
-        Enum.reduce(primary_keys, [resource], &(&2 ++ [Map.get(dump_value, &1)]))
+  def unique_id(%{__struct__: resource} = struct, dump_value) do
+    if Ash.Resource.Info.resource?(resource) do
+      case Ash.Resource.Info.primary_key(resource) do
+        [] ->
+          nil
+
+        primary_keys ->
+          Enum.reduce(primary_keys, [resource], &(&2 ++ [Map.get(dump_value, &1)]))
+      end
+    else
+      # For non-Ash structs (Time, Date, DateTime, Decimal, etc.),
+      # return the struct itself for value-based equality matching
+      struct
     end
   end
 
diff --git a/test/ash_paper_trail/full_diff_test.exs b/test/ash_paper_trail/full_diff_test.exs
index f2220fa..bc98cb2 100644
--- a/test/ash_paper_trail/full_diff_test.exs
+++ b/test/ash_paper_trail/full_diff_test.exs
@@ -932,4 +932,39 @@ defmodule AshPaperTrail.FullDiffTest do
              } = last_version_changes(ctx.domain, ctx.version_resource)
     end
   end
+
+  describe "full_diff with primitive struct types" do
+    test "create with {:array, :time} attribute", ctx do
+      ctx.resource.create!(%{
+        subject: "Schedule",
+        times: [~T[08:00:00], ~T[10:00:00], ~T[12:00:00]]
+      })
+
+      assert %{
+               times: %{
+                 to: [
+                   %{added: ~T[08:00:00], index: %{to: 0}},
+                   %{added: ~T[10:00:00], index: %{to: 1}},
+                   %{added: ~T[12:00:00], index: %{to: 2}}
+                 ]
+               }
+             } = last_version_changes(ctx.domain, ctx.version_resource)
+    end
+
+    test "update {:array, :time} with reorder, add, and remove", ctx do
+      post = ctx.resource.create!(%{subject: "Schedule", times: [~T[08:00:00], ~T[10:00:00]]})
+
+      ctx.resource.update!(post, %{times: [~T[10:00:00], ~T[08:00:00], ~T[14:00:00]]})
+
+      assert %{
+               times: %{
+                 to: [
+                   %{unchanged: ~T[10:00:00], index: %{from: 1, to: 0}},
+                   %{unchanged: ~T[08:00:00], index: %{from: 0, to: 1}},
+                   %{added: ~T[14:00:00], index: %{to: 2}}
+                 ]
+               }
+             } = last_version_changes(ctx.domain, ctx.version_resource)
+    end
+  end
 end
diff --git a/test/support/posts/full_diff_post.ex b/test/support/posts/full_diff_post.ex
index 3e925cf..e7579b7 100644
--- a/test/support/posts/full_diff_post.ex
+++ b/test/support/posts/full_diff_post.ex
@@ -104,5 +104,10 @@ defmodule AshPaperTrail.Test.Posts.FullDiffPost do
       public? true
       allow_nil? true
     end
+
+    attribute :times, {:array, :time} do
+      public? true
+      allow_nil? true
+    end
   end
 end