Fix input_datetime.set_datetime not accepting 0 timestamp value (#134489)

tests/components/input_datetime/test_init.py

@@ -217,6 +217,34 @@ async def test_set_datetime_3(hass: HomeAssistant) -> None:
     assert state.attributes["timestamp"] == dt_obj.timestamp()
 
 
+async def test_set_datetime_4(hass: HomeAssistant) -> None:
+    """Test set_datetime method using timestamp 0."""
+    await async_setup_component(
+        hass, DOMAIN, {DOMAIN: {"test_datetime": {"has_time": True, "has_date": True}}}
+    )
+
+    entity_id = "input_datetime.test_datetime"
+
+    dt_obj = datetime.datetime(
+        1969, 12, 31, 16, 00, 00, tzinfo=dt_util.get_time_zone(hass.config.time_zone)
+    )
+
+    await async_set_timestamp(hass, entity_id, 0)
+
+    state = hass.states.get(entity_id)
+    assert state.state == dt_obj.strftime(FORMAT_DATETIME)
+    assert state.attributes["has_time"]
+    assert state.attributes["has_date"]
+
+    assert state.attributes["year"] == 1969
+    assert state.attributes["month"] == 12
+    assert state.attributes["day"] == 31
+    assert state.attributes["hour"] == 16
+    assert state.attributes["minute"] == 00
+    assert state.attributes["second"] == 0
+    assert state.attributes["timestamp"] == 0
+
+
 async def test_set_datetime_time(hass: HomeAssistant) -> None:
     """Test set_datetime method with only time."""
     await async_setup_component(