From eef7ce5c807cc5701e88dff4182690fda907d974 Mon Sep 17 00:00:00 2001
From: santhreal <64453045+santhreal@users.noreply.github.com>
Date: Fri, 17 Jul 2026 22:26:20 -0700
Subject: [PATCH] fix: render non-date DateTimeField data without
 AttributeError

Initial data= or obj string values for date/time fields used to crash in
_value via a missing strftime. Render the string for the widget instead,
including DateTimeLocalField.
---
 CHANGES.rst                        |  4 ++++
 src/wtforms/fields/datetime.py     | 11 +++++++++--
 tests/fields/test_date.py          | 11 +++++++++++
 tests/fields/test_datetimelocal.py |  8 ++++++++
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 423e04b8..5dc673d0 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,6 +5,10 @@ Version 3.3.0b4
 
 Unreleased
 
+- :meth:`~fields.DateTimeField._value` and
+  :meth:`~fields.DateTimeLocalField._value` render plain string ``data`` /
+  ``obj`` values instead of raising ``AttributeError``.
+
 - :class:`~datalist.DataList` ``choices`` accepts the shorthand
   ``{value: label}`` dict syntax. :issue:`886`
 - ``choices`` callables on fields nested in a :class:`~fields.FieldList` are
diff --git a/src/wtforms/fields/datetime.py b/src/wtforms/fields/datetime.py
index 4158dd3b..e98ce545 100644
--- a/src/wtforms/fields/datetime.py
+++ b/src/wtforms/fields/datetime.py
@@ -57,8 +57,13 @@ def __init__(
     def _value(self):
         if self.raw_data:
             return " ".join(self.raw_data)
+        if not self.data:
+            return ""
         format = self.format[0]
-        return self.data and self.data.strftime(format) or ""
+        # data=/obj may supply a plain string; still render for the widget.
+        if not hasattr(self.data, "strftime"):
+            return str(self.data)
+        return self.data.strftime(format)
 
     def process_formdata(self, valuelist):
         if not valuelist:
@@ -279,8 +284,10 @@ def _value(self):
             return ""
 
         value = self.data
+        if not hasattr(value, "strftime"):
+            return str(value)
         tz = self._resolve_tz()
-        if tz is not None and value.tzinfo is not None:
+        if tz is not None and getattr(value, "tzinfo", None) is not None:
             value = value.astimezone(tz).replace(tzinfo=None)
 
         return value.strftime(self.format[0])
diff --git a/tests/fields/test_date.py b/tests/fields/test_date.py
index ecc729cd..ab4488c1 100644
--- a/tests/fields/test_date.py
+++ b/tests/fields/test_date.py
@@ -38,3 +38,14 @@ class G(Form):
     form = G(DummyPostData(a=["bogus"]))
     assert not form.validate()
     assert form.a.errors == ["Enter a date as YYYY-MM-DD."]
+
+
+def test_initial_string_data_renders():
+    form = F(data={"a": "2020-01-02"})
+    assert form.a.data == "2020-01-02"
+    assert form.a._value() == "2020-01-02"
+
+
+def test_initial_non_date_obj_attribute_renders():
+    form = F(obj=type("O", (), {"a": "not-a-date"})())
+    assert form.a._value() == "not-a-date"
diff --git a/tests/fields/test_datetimelocal.py b/tests/fields/test_datetimelocal.py
index 1b8ed747..d3390cf9 100644
--- a/tests/fields/test_datetimelocal.py
+++ b/tests/fields/test_datetimelocal.py
@@ -139,3 +139,11 @@ def test_tz_naive_data_rendered_unchanged():
     F = make_form(a=DateTimeLocalField(tz=paris))
     form = F(a=datetime(2026, 5, 6, 16, 0))
     assert form.a._value() == "2026-05-06 16:00:00"
+
+
+def test_initial_string_data_renders():
+    class G(Form):
+        a = DateTimeLocalField()
+
+    form = G(data={"a": "2020-01-02T03:04"})
+    assert form.a._value() == "2020-01-02T03:04"