From 14d1c5aa1c2da3510e404210033f8955637cc966 Mon Sep 17 00:00:00 2001
From: youdie006 <xncb135@korea.ac.kr>
Date: Tue, 15 Sep 2026 14:06:49 +0900
Subject: [PATCH] Normalize DateTime casts to UTC for :time and :time_usec

#4775 moved :date, :naive_datetime and :naive_datetime_usec onto the UTC
instant when given a non-UTC %DateTime{}, but cast_time/1 has no %DateTime{}
clause, so it falls through to the map clauses and rebuilds a Time from the
wall-clock fields.

That leaves a schema casting one %DateTime{} into a :date field and a :time
field with 2020-05-31 and 00:30:07, which is neither the UTC instant nor the
submitted local time. Route %DateTime{} through cast_utc_datetime/1 first, the
same way cast_date/1 and cast_naive_datetime/1 do.
---
 CHANGELOG.md            | 1 +
 lib/ecto/type.ex        | 7 +++++++
 test/ecto/type_test.exs | 5 +++++
 3 files changed, 13 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8abd9341bd..c3b0e76bff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 
   * [Ecto.Query] Fix subqueries in interpolated join filters (this changes the representation of `JoinExpr.on` fields to a `BooleanExpr`)
   * [Ecto.Query] Fix selecting lists of fields and using `map/2` from subqueries
+  * [Ecto.Type] Normalize `DateTime` casts to UTC for `:time` and `:time_usec`
 
 ## v3.14.2 (2026-08-14)
 
diff --git a/lib/ecto/type.ex b/lib/ecto/type.ex
index f697dc562f..107cafce71 100644
--- a/lib/ecto/type.ex
+++ b/lib/ecto/type.ex
@@ -1114,6 +1114,13 @@ defmodule Ecto.Type do
     end
   end
 
+  defp cast_time(%DateTime{} = datetime) do
+    case cast_utc_datetime(datetime) do
+      {:ok, datetime} -> {:ok, DateTime.to_time(datetime)}
+      :error -> :error
+    end
+  end
+
   defp cast_time(%{"hour" => empty, "minute" => empty}) when empty in ["", nil],
     do: {:ok, nil}
 
diff --git a/test/ecto/type_test.exs b/test/ecto/type_test.exs
index f2bc5aafe3..b84aa03961 100644
--- a/test/ecto/type_test.exs
+++ b/test/ecto/type_test.exs
@@ -532,6 +532,9 @@ defmodule Ecto.TypeTest do
 
       assert Ecto.Type.cast(:time, ~D[2016-11-11]) ==
                :error
+
+      assert Ecto.Type.cast(:time, @non_utc_datetime) ==
+               {:ok, ~T[22:30:07]}
     end
 
     test "dump" do
@@ -607,6 +610,8 @@ defmodule Ecto.TypeTest do
     test "cast from DateTime" do
       utc_datetime = DateTime.from_naive!(~N[2016-11-11 23:30:10], "Etc/UTC")
       assert Ecto.Type.cast(:time_usec, utc_datetime) == {:ok, ~T[23:30:10.000000]}
+
+      assert Ecto.Type.cast(:time_usec, @non_utc_datetime) == {:ok, ~T[22:30:07.008000]}
     end
 
     test "cast from Date" do