Add timezone_select() usage

Author: MGatner

user_guide_src/source/helpers/date_helper.rst

@@ -43,5 +43,21 @@ The following functions are available:
 	If a timezone is not provided, it will return ``time()`` based on the
 	**time_reference** setting.
 
+.. php:function:: timezone_select([$class = '', $default = '', $what = \DateTimeZone::ALL, $country = null])
+
+	:param	string	$class: Optional class to apply to the select field
+	:param	string	$default: Default value for initial selection
+	:param	string	$what: DateTimeZone class constants (see `listIdentifiers <https://www.php.net/manual/en/datetimezone.listidentifiers.php>`_)
+	:param	string	$country: A two-letter ISO 3166-1 compatible country code (see `listIdentifiers <https://www.php.net/manual/en/datetimezone.listidentifiers.php>`_)
+	:returns:	Preformatted HTML select field
+	:rtype:	string
+
+	Generates a `select` form field of available timezones (optionally filtered by `$what` and `$country`).
+	You can supply an option class to apply to the field to make formatting easier, as well as a default
+	selected value.
+	::
+
+		echo timezone_select('custom-select', 'America/New_York');
+
 Many functions previously found in the CodeIgniter 3 ``date_helper`` have been moved to the ``I18n``
 module in CodeIgniter 4.