diff --git a/Readme.md b/Readme.md
index 7dcdbed..025abb0 100644
--- a/Readme.md
+++ b/Readme.md
@@ -96,6 +96,7 @@ Mask | Description
 `MM` | Minutes; leading zero for single-digit minutes.
 `N` | ISO 8601 numeric representation of the day of the week.
 `o` | GMT/UTC timezone offset, e.g. -0500 or +0230.
+`p` | GMT/UTC timezone offset, e.g. -05:00 or +02:30.
 `s` | Seconds; no leading zero for single-digit seconds.
 `ss` | Seconds; leading zero for single-digit seconds.
 `S` | The date's ordinal suffix (st, nd, rd, or th). Works well with `d`.
@@ -124,7 +125,7 @@ Name | Mask | Example
 `longTime` | `h:MM:ss TT Z` | 5:46:21 PM EST
 `isoDate` | `yyyy-mm-dd` | 2007-06-09
 `isoTime` | `HH:MM:ss` | 17:46:21
-`isoDateTime` | `yyyy-mm-dd'T'HH:MM:ss` | 2007-06-09T17:46:21
+`isoDateTime` | `yyyy-mm-dd'T'HH:MM:sso` | 2007-06-09T17:46:21+0700
 `isoUtcDateTime` | `UTC:yyyy-mm-dd'T'HH:MM:ss'Z'` | 2007-06-09T22:46:21Z
 
 ### Localization
diff --git a/lib/dateformat.js b/lib/dateformat.js
index 95ed91b..7ae6cc1 100644
--- a/lib/dateformat.js
+++ b/lib/dateformat.js
@@ -16,7 +16,7 @@
   'use strict';
 
   var dateFormat = (function() {
-      var token = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|[LloSZWN]|"[^"]*"|'[^']*'/g;
+      var token = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|[LlopSZWN]|"[^"]*"|'[^']*'/g;
       var timezone = /\b(?:[PMCEA][SDP]T|(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time|(?:GMT|UTC)(?:[-+]\d{4})?)\b/g;
       var timezoneClip = /[^-+\dA-Z]/g;
   
@@ -90,6 +90,7 @@
           TT:   H < 12 ? dateFormat.i18n.timeNames[6] : dateFormat.i18n.timeNames[7],
           Z:    gmt ? 'GMT' : utc ? 'UTC' : (String(date).match(timezone) || ['']).pop().replace(timezoneClip, ''),
           o:    (o > 0 ? '-' : '+') + pad(Math.floor(Math.abs(o) / 60) * 100 + Math.abs(o) % 60, 4),
+          p:    (o > 0 ? '-' : '+') + pad(Math.floor(Math.abs(o) / 60),2) + ':' + pad(Math.floor(Math.abs(o) % 60), 2),
           S:    ['th', 'st', 'nd', 'rd'][d % 10 > 3 ? 0 : (d % 100 - d % 10 != 10) * d % 10],
           W:    W,
           N:    N
diff --git a/test/test_tzdatetime.js b/test/test_tzdatetime.js
new file mode 100644
index 0000000..d0c290c
--- /dev/null
+++ b/test/test_tzdatetime.js
@@ -0,0 +1,12 @@
+var assert = require('assert');
+
+var dateFormat = require('./../lib/dateformat');
+
+describe('isoUtcDateTime', function() {
+  it('should correctly format the timezone part', function(done) {
+    var actual = dateFormat('2014-06-02T13:23:21-08:00', 'yyyy-mm-dd\'T\'HH:MM:ssp');
+    var actual2 = dateFormat('2014-06-02T13:23:21-08:00', 'yyyy-mm-dd\'T\'HH:MM:sso');
+    assert.strictEqual(actual, actual2.replace(/(\d\d)$/, ':$1'));
+    done();
+  });
+});