Updates documentation

Author: sdispater

docs/_docs/instantiation.rst

@@ -18,6 +18,12 @@ You'll notice above that the timezone (2nd) parameter was passed as a string and
 rather than a ``tzinfo`` instance. All timezone parameters have been augmented
 so you can pass a ``tzinfo`` instance, string or integer offset to GMT
 and the timezone will be created for you.
+
+.. note::
+
+    Supported strings for timezones are the one provided by the `IANA time zone database <https://www.iana.org/time-zones>`_.
+    The special ``local`` string is also supported and will return your current timezone.
+
 This is again shown in the next example which also introduces the ``now()`` function.
 
 .. code-block:: python