diff --git a/postmark/models.py b/postmark/models.py
index 23997b6..a97ce09 100755
--- a/postmark/models.py
+++ b/postmark/models.py
@@ -5,6 +5,7 @@
 from datetime import datetime
 from pytz import timezone
 import pytz
+import iso8601
 
 from postmark.signals import post_send
 
@@ -101,16 +102,10 @@ def sent_message(sender, **kwargs):
         
         if not recipient[0]:
             continue
-        
-        timestamp, tz = resp["SubmittedAt"].rsplit("+", 1)
-        tz_offset = int(tz.split(":", 1)[0])
-        tz = timezone("Etc/GMT%s%d" % ("+" if tz_offset >= 0 else "-", tz_offset))
-        submitted_at = tz.localize(datetime.strptime(timestamp[:26], POSTMARK_DATETIME_STRING)).astimezone(pytz.utc)
-        
-        
+
         emsg = EmailMessage(
             message_id=resp["MessageID"],
-            submitted_at=submitted_at,
+            submitted_at=iso8601.parse_date(resp["SubmittedAt"]),
             status=resp["Message"],
             to=recipient[0],
             to_type=recipient[1],
@@ -123,4 +118,4 @@ def sent_message(sender, **kwargs):
             headers=msg.get("Headers", ""),
             attachments=msg.get("Attachments", "")
         )
-        emsg.save()
\ No newline at end of file
+        emsg.save()
diff --git a/setup.py b/setup.py
index 32eb52f..9c82b33 100644
--- a/setup.py
+++ b/setup.py
@@ -12,6 +12,7 @@
     install_requires = [
         "httplib2",
         "pytz",
+        "iso8601",
     ],
     packages = [
         "postmark",