use `isoformat()` in jsonutil

allows preservation of timezone info.

Timezone info is still ignored in the extract-dates part, for now.

IPython/utils/jsonutil.py

@@ -33,7 +33,7 b" next_attr_name = '__next__' if py3compat.PY3 else 'next'"
 
 # timestamp formats
 ISO8601="%Y-%m-%dT%H:%M:%S.%f"
-ISO8601_PAT=re.compile(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+$")
+ISO8601_PAT=re.compile(r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+(Z?[\+\-]\d{2}:?\d{2})?$")
 
 #-----------------------------------------------------------------------------
 # Classes and functions
@@ -72,7 +72,9 b' def extract_dates(obj):'
         obj = [ extract_dates(o) for o in obj ]
     elif isinstance(obj, basestring):
         if ISO8601_PAT.match(obj):
-            obj = datetime.strptime(obj, ISO8601)
+            # FIXME: add actual timezone support
+            notz = obj.split('Z',1)[0]
+            obj = datetime.strptime(notz, ISO8601)
     return obj
 
 def squash_dates(obj):
@@ -84,13 +86,13 b' def squash_dates(obj):'
     elif isinstance(obj, (list, tuple)):
         obj = [ squash_dates(o) for o in obj ]
     elif isinstance(obj, datetime):
-        obj = obj.strftime(ISO8601)
+        obj = obj.isoformat()
     return obj
 
 def date_default(obj):
     """default function for packing datetime objects in JSON."""
     if isinstance(obj, datetime):
-        return obj.strftime(ISO8601)
+        return obj.isoformat()
     else:
         raise TypeError("%r is not JSON serializable"%obj)