Fixed changes requested by @srenatus (squash before merge)

Updating docs for built-in functions.

Signed-off-by: Johan Fylling <johan.dev@fylling.se>

docs/content/policy-reference.md

@@ -800,13 +800,13 @@ result_valid_hs256 := io.jwt.verify_hs256(result_hs256, "foo")
 | Built-in | Description | Wasm Support |
 | ------- |-------------|---------------|
 | <span class="opa-keep-it-together">``output := time.now_ns()``</span> | ``output`` is a ``number`` representing the current time since epoch in nanoseconds. | ``SDK-dependent`` |
-| <span class="opa-keep-it-together">``output := time.parse_ns(layout, value)``</span> | ``output`` is a ``number`` representing the time ``value`` in nanoseconds since epoch. See the [Go `time` package documentation](https://golang.org/pkg/time/#Parse) for more details on ``layout``. | ``SDK-dependent`` |
-| <span class="opa-keep-it-together">``output := time.parse_rfc3339_ns(value)``</span> | ``output`` is a ``number`` representing the time ``value`` in nanoseconds since epoch. | ``SDK-dependent`` |
+| <span class="opa-keep-it-together">``output := time.parse_ns(layout, value)``</span> | ``output`` is a ``number`` representing the time ``value`` in nanoseconds since epoch; or ``undefined`` if outside the valid time range that can fit within an ``int64``. See the [Go `time` package documentation](https://golang.org/pkg/time/#Parse) for more details on ``layout``. | ``SDK-dependent`` |
+| <span class="opa-keep-it-together">``output := time.parse_rfc3339_ns(value)``</span> | ``output`` is a ``number`` representing the time ``value`` in nanoseconds since epoch; or ``undefined`` if outside the valid time range that can fit within an ``int64``. | ``SDK-dependent`` |
 | <span class="opa-keep-it-together">``output := time.parse_duration_ns(duration)``</span> | ``output`` is a ``number`` representing the duration ``duration`` in nanoseconds. See the [Go `time` package documentation](https://golang.org/pkg/time/#ParseDuration) for more details on ``duration``. | ``SDK-dependent`` |
 | <span class="opa-keep-it-together">``output := time.date(ns)``<br/>``output := time.date([ns, tz])``</span> | ``output`` is of the form ``[year, month, day]``, which includes the ``year``, ``month`` (0-12), and ``day`` (0-31) as ``number``s representing the date from the nanoseconds since epoch (``ns``) in the timezone (``tz``), if supplied, or as UTC.| ``SDK-dependent`` |
 | <span class="opa-keep-it-together">``output := time.clock(ns)``<br/>``output := time.clock([ns, tz])``</span> | ``output`` is of the form ``[hour, minute, second]``, which outputs the ``hour``, ``minute`` (0-59), and ``second`` (0-59) as ``number``s representing the time of day for the nanoseconds since epoch (``ns``) in the timezone (``tz``), if supplied, or as UTC. | ``SDK-dependent`` |
 | <span class="opa-keep-it-together">``day := time.weekday(ns)``<br/>``day := time.weekday([ns, tz])``</span> | outputs the ``day`` as ``string`` representing the day of the week for the nanoseconds since epoch (``ns``) in the timezone (``tz``), if supplied, or as UTC. | ``SDK-dependent`` |
-| <span class="opa-keep-it-together">``output := time.add_date(ns, years, months, days)``</span> | ``output`` is a ``number`` representing the time since epoch in nanoseconds after adding the ``years``, ``months`` and ``days`` to ``ns``. See the [Go `time` package documentation](https://golang.org/pkg/time/#Time.AddDate) for more details on ``add_date``. | ``SDK-dependent`` |
+| <span class="opa-keep-it-together">``output := time.add_date(ns, years, months, days)``</span> | ``output`` is a ``number`` representing the time since epoch in nanoseconds after adding the ``years``, ``months`` and ``days`` to ``ns``; or ``undefined`` if outside the valid time range that can fit within an ``int64``. See the [Go `time` package documentation](https://golang.org/pkg/time/#Time.AddDate) for more details on ``add_date``. | ``SDK-dependent`` |
 | <span class="opa-keep-it-together">``output := time.diff(ns1, ns2)``<br/>``output := time.diff([ns1, tz1], [ns2, tz2])``</span> | ``output`` is of the form ``[year(s), month(s), day(s), hour(s), minute(s), second(s)]``, which outputs ``year(s)``, ``month(s)`` (0-11), ``day(s)`` (0-30),  ``hour(s)``(0-23), ``minute(s)``(0-59) and ``second(s)``(0-59)  as ``number``s representing the  difference between the the two timestamps in nanoseconds since epoch (``ns1`` and ``ns2``), in the timezones (``tz1`` and ``tz2``, respectively), if supplied, or as UTC. | ``SDK-dependent`` |
 
 > Multiple calls to the `time.now_ns` built-in function within a single policy