diff --git a/datafusion/sql/src/planner.rs b/datafusion/sql/src/planner.rs
index a3e6d75fdbfac..bb7347e6396d2 100644
--- a/datafusion/sql/src/planner.rs
+++ b/datafusion/sql/src/planner.rs
@@ -775,7 +775,13 @@ impl<'a, S: ContextProvider> SqlToRel<'a, S> {
                 {
                     // Timestamp With Time Zone
                     // INPUT : [SQLDataType]   TimestampTz + [Config] Time Zone
-                    // OUTPUT: [ArrowDataType] Timestamp<TimeUnit, Some(Time Zone)>
+                    // OUTPUT: [ArrowDataType] Timestamp<TimeUnit, Time Zone>
+                    //
+                    // Note that the configured time zone is an `Option` that is
+                    // unset by default, so by default this yields the
+                    // timezone-naive `Timestamp<TimeUnit, None>`. Whether that
+                    // should remain the behavior is tracked in
+                    // https://github.com/apache/datafusion/issues/25166
                     self.context_provider.options().execution.time_zone.clone()
                 } else {
                     // Timestamp Without Time zone
diff --git a/docs/source/user-guide/sql/data_types.md b/docs/source/user-guide/sql/data_types.md
index 2e75fce6c7aa9..9d2fe3e6e8060 100644
--- a/docs/source/user-guide/sql/data_types.md
+++ b/docs/source/user-guide/sql/data_types.md
@@ -105,12 +105,37 @@ The maximum supported precision for `DECIMAL` types is 76.
 
 ## Date/Time Types
 
-| SQL DataType | Arrow DataType                   |
-| ------------ | :------------------------------- |
-| `DATE`       | `Date32`                         |
-| `TIME`       | `Time64(Nanosecond)`             |
-| `TIMESTAMP`  | `Timestamp(Nanosecond, None)`    |
-| `INTERVAL`   | `Interval(IntervalMonthDayNano)` |
+| SQL DataType                                               | Arrow DataType                                             |
+| ---------------------------------------------------------- | :--------------------------------------------------------- |
+| `DATE`                                                     | `Date32`                                                   |
+| `TIME`                                                     | `Time64(Nanosecond)`                                       |
+| `TIMESTAMP`, `TIMESTAMP(p)`, `TIMESTAMP WITHOUT TIME ZONE` | `Timestamp(unit, None)`                                    |
+| `TIMESTAMPTZ(p)`, `TIMESTAMP(p) WITH TIME ZONE`            | `Timestamp(unit, None)` by default — see the warning below |
+| `INTERVAL`                                                 | `Interval(IntervalMonthDayNano)`                           |
+
+:::{warning}
+`TIMESTAMPTZ` and `TIMESTAMP WITH TIME ZONE` do **not** give a timezone-aware
+type by default. The zone comes from the
+[`datafusion.execution.time_zone`] setting, and that setting is unset unless you
+set it. So `'2024-01-01T12:00:00Z'::timestamptz` gives `Timestamp(unit, None)`
+by default, and DataFusion discards the `Z`.
+
+This is a known bug. See [issue #25166]. PostgreSQL and DuckDB always give an
+aware type here, because their session time zone always has a value.
+
+Set `datafusion.execution.time_zone` to make these types aware. `'UTC'` is a
+good value.
+:::
+
+`unit` comes from the optional precision `p` on the two `TIMESTAMP` rows. Use
+`0`, `3`, `6` or `9` for `Second`, `Millisecond`, `Microsecond` or `Nanosecond`.
+DataFusion rejects each other value of `p`. If you omit `p`, the unit is
+`Nanosecond`. The precision goes after `TIMESTAMPTZ`, but before
+`WITH TIME ZONE`: use `TIMESTAMPTZ(3)` or `TIMESTAMP(3) WITH TIME ZONE`.
+`DATE`, `TIME` and `INTERVAL` do not accept a precision.
+
+[`datafusion.execution.time_zone`]: ../configs.md
+[issue #25166]: https://github.com/apache/datafusion/issues/25166
 
 ## Boolean Types