From 0b667c661a40acd22c6b12c323d31c84541a6701 Mon Sep 17 00:00:00 2001
From: Huanyi Xie <74809554+xiehuanyi@users.noreply.github.com>
Date: Mon, 12 Oct 2026 22:37:17 +0300
Subject: [PATCH] Preserve date serialization and trivia for reflected addition

---
 CHANGELOG.md        |  2 ++
 tests/test_items.py | 21 +++++++++++++++++++++
 tomlkit/items.py    |  4 ++++
 3 files changed, 27 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0af52c54..0b2c2170 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 ### Fixed
 
+- Preserve date text and temporal trivia when adding a timedelta from the left to `Date` or `DateTime` values.
+
 - Fix valid TOML being rejected when an out-of-order table reopens an implicit super-table with a dotted key: `[a.b.c]` then `[a]` with `b.z = 1` extends the implicit `a.b` super-table rather than redefining it (stdlib `tomllib` accepts it), so it now parses and round-trips instead of raising `Redefinition of an existing table`. The concrete-table case (`[a.b]` then `[a]` `b.z = 1`) stays rejected. ([#565](https://github.com/python-poetry/tomlkit/pull/565))
 - Fix appending a key to a parsed inline table that uses `", "` separators emitting a bare `","` for the new entry, leaving the table inconsistently spaced (e.g. `{x = 1, y = 2,z = 3}`). ([#595](https://github.com/python-poetry/tomlkit/pull/595))
 
diff --git a/tests/test_items.py b/tests/test_items.py
index bbe1b2ed..a61902b6 100644
--- a/tests/test_items.py
+++ b/tests/test_items.py
@@ -803,6 +803,27 @@ def test_datetimes_behave_like_datetimes(tz_utc: tzinfo, tz_pst: tzinfo) -> None
     assert doc.as_string() == "dt = 2018-07-23T12:34:56-05:00"
 
 
+@pytest.mark.parametrize(
+    "literal", ["2024-02-28", "2024-02-28T10:00:00", "2024-02-28T10:00:00Z"]
+)
+@pytest.mark.parametrize("delta", [timedelta(days=1), timedelta(days=-1)])
+def test_reflected_temporal_addition_preserves_serialization(
+    literal: str, delta: timedelta
+) -> None:
+    doc = parse(f"when = {literal} # birthday\n")
+    value = doc["when"]
+    expected = value + delta
+
+    result = delta + value
+
+    assert type(result) is type(value)
+    assert result.unwrap() == expected.unwrap()
+    assert result.as_string() == expected.as_string()
+    assert result.trivia == expected.trivia
+    doc["when"] = result
+    assert parse(doc.as_string())["when"] == expected
+
+
 @pytest.mark.parametrize("fold", [0, 1])
 def test_datetime_subtraction_preserves_input_fold(tz_fold: tzinfo, fold: int) -> None:
     value = datetime(2018, 11, 4, 1, 30, tzinfo=tz_fold, fold=fold)
diff --git a/tomlkit/items.py b/tomlkit/items.py
index 26b01097..076b5f9d 100644
--- a/tomlkit/items.py
+++ b/tomlkit/items.py
@@ -1151,6 +1151,8 @@ def __add__(self, other: timedelta) -> DateTime:
 
         return self._new(result)
 
+    __radd__ = __add__
+
     @overload  # type: ignore[override]
     def __sub__(self, other: timedelta) -> DateTime: ...
 
@@ -1271,6 +1273,8 @@ def __add__(self, other: timedelta) -> Date:
 
         return self._new(result)
 
+    __radd__ = __add__
+
     @overload  # type: ignore[override]
     def __sub__(self, other: timedelta) -> Date: ...