Updates readme per comment from @fzaninotto

readme.md

@@ -180,13 +180,13 @@ Each of the generator properties (like `name`, `address`, and `lorem`) are calle
 ### `Faker\Provider\DateTime`
 
     unixTime($max = 'now')                // 58781813
-    dateTime($max = 'now')                // DateTime('2008-04-25 08:37:17')
-    dateTimeAD($max = 'now')              // DateTime('1800-04-29 20:38:49')
+    dateTime($max = 'now', $timezone = date_default_timezone_get()) // DateTime('2008-04-25 08:37:17', 'UTC')
+    dateTimeAD($max = 'now', $timezone = date_default_timezone_get()) // DateTime('1800-04-29 20:38:49', 'Europe/Paris')
     iso8601($max = 'now')                 // '1978-12-09T10:10:29+0000'
     date($format = 'Y-m-d', $max = 'now') // '1979-06-09'
     time($format = 'H:i:s', $max = 'now') // '20:49:42'
-    dateTimeBetween($startDate = '-30 years', $endDate = 'now') // DateTime('2003-03-15 02:00:49')
-    dateTimeInInterval($startDate = '-30 years', $interval = '+ 5 days') // DateTime('2003-03-15 02:00:49')
+    dateTimeBetween($startDate = '-30 years', $endDate = 'now', $timezone = date_default_timezone_get()) // DateTime('2003-03-15 02:00:49', 'Africa/Lagos')
+    dateTimeInInterval($startDate = '-30 years', $interval = '+ 5 days', $timezone = date_default_timezone_get()) // DateTime('2003-03-15 02:00:49', 'Antartica/Vostok')
     dateTimeThisCentury($max = 'now')     // DateTime('1915-05-30 19:28:21')
     dateTimeThisDecade($max = 'now')      // DateTime('2007-05-29 22:30:48')
     dateTimeThisYear($max = 'now')        // DateTime('2011-02-27 20:52:14')