diff --git a/keystone/openstack/common/timeutils.py b/keystone/openstack/common/timeutils.py
index 86004391de..8e40660f6a 100644
--- a/keystone/openstack/common/timeutils.py
+++ b/keystone/openstack/common/timeutils.py
@@ -25,18 +25,22 @@ import datetime
 import iso8601
 
 
-TIME_FORMAT = "%Y-%m-%dT%H:%M:%S"
-PERFECT_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S.%f"
+# ISO 8601 extended time format with microseconds
+_ISO8601_TIME_FORMAT_SUBSECOND = '%Y-%m-%dT%H:%M:%S.%f'
+_ISO8601_TIME_FORMAT = '%Y-%m-%dT%H:%M:%S'
+PERFECT_TIME_FORMAT = _ISO8601_TIME_FORMAT_SUBSECOND
 
 
-def isotime(at=None):
+def isotime(at=None, subsecond=False):
     """Stringify time in ISO 8601 format"""
     if not at:
         at = utcnow()
-    str = at.strftime(TIME_FORMAT)
+    st = at.strftime(_ISO8601_TIME_FORMAT
+                     if not subsecond
+                     else _ISO8601_TIME_FORMAT_SUBSECOND)
     tz = at.tzinfo.tzname(None) if at.tzinfo else 'UTC'
-    str += ('Z' if tz == 'UTC' else tz)
-    return str
+    st += ('Z' if tz == 'UTC' else tz)
+    return st
 
 
 def parse_isotime(timestr):
@@ -71,11 +75,15 @@ def normalize_time(timestamp):
 
 def is_older_than(before, seconds):
     """Return True if before is older than seconds."""
+    if isinstance(before, basestring):
+        before = parse_strtime(before).replace(tzinfo=None)
     return utcnow() - before > datetime.timedelta(seconds=seconds)
 
 
 def is_newer_than(after, seconds):
     """Return True if after is newer than seconds."""
+    if isinstance(after, basestring):
+        after = parse_strtime(after).replace(tzinfo=None)
     return after - utcnow() > datetime.timedelta(seconds=seconds)
 
 
@@ -87,22 +95,37 @@ def utcnow_ts():
 def utcnow():
     """Overridable version of utils.utcnow."""
     if utcnow.override_time:
-        return utcnow.override_time
+        try:
+            return utcnow.override_time.pop(0)
+        except AttributeError:
+            return utcnow.override_time
     return datetime.datetime.utcnow()
 
 
+def iso8601_from_timestamp(timestamp):
+    """Returns a iso8601 formated date from timestamp"""
+    return isotime(datetime.datetime.utcfromtimestamp(timestamp))
+
+
 utcnow.override_time = None
 
 
 def set_time_override(override_time=datetime.datetime.utcnow()):
-    """Override utils.utcnow to return a constant time."""
+    """
+    Override utils.utcnow to return a constant time or a list thereof,
+    one at a time.
+    """
     utcnow.override_time = override_time
 
 
 def advance_time_delta(timedelta):
     """Advance overridden time using a datetime.timedelta."""
     assert(not utcnow.override_time is None)
-    utcnow.override_time += timedelta
+    try:
+        for dt in utcnow.override_time:
+            dt += timedelta
+    except TypeError:
+        utcnow.override_time += timedelta
 
 
 def advance_time_seconds(seconds):
@@ -135,3 +158,29 @@ def unmarshall_time(tyme):
                              minute=tyme['minute'],
                              second=tyme['second'],
                              microsecond=tyme['microsecond'])
+
+
+def delta_seconds(before, after):
+    """
+    Compute the difference in seconds between two date, time, or
+    datetime objects (as a float, to microsecond resolution).
+    """
+    delta = after - before
+    try:
+        return delta.total_seconds()
+    except AttributeError:
+        return ((delta.days * 24 * 3600) + delta.seconds +
+                float(delta.microseconds) / (10 ** 6))
+
+
+def is_soon(dt, window):
+    """
+    Determines if time is going to happen in the next window seconds.
+
+    :params dt: the time
+    :params window: minimum seconds to remain to consider the time not soon
+
+    :return: True if expiration is within the given duration
+    """
+    soon = (utcnow() + datetime.timedelta(seconds=window))
+    return normalize_time(dt) <= soon