diff --git a/swift/common/middleware/s3api/controllers/bucket.py b/swift/common/middleware/s3api/controllers/bucket.py
index e9b0fdf54e..c9443fa977 100644
--- a/swift/common/middleware/s3api/controllers/bucket.py
+++ b/swift/common/middleware/s3api/controllers/bucket.py
@@ -34,7 +34,7 @@ from swift.common.middleware.s3api.s3response import \
     MalformedXML, InvalidLocationConstraint, NoSuchBucket, \
     BucketNotEmpty, VersionedBucketNotEmpty, InternalError, \
     ServiceUnavailable, NoSuchKey
-from swift.common.middleware.s3api.utils import MULTIUPLOAD_SUFFIX
+from swift.common.middleware.s3api.utils import MULTIUPLOAD_SUFFIX, S3Timestamp
 
 MAX_PUT_BUCKET_BODY_SIZE = 10240
 
@@ -291,7 +291,7 @@ class BucketController(Controller):
             contents = SubElement(elem, 'Contents')
             SubElement(contents, 'Key').text = name
         SubElement(contents, 'LastModified').text = \
-            o['last_modified'][:-3] + 'Z'
+            S3Timestamp.from_isoformat(o['last_modified']).s3xmlformat
         if contents.tag != 'DeleteMarker':
             if 's3_etag' in o:
                 # New-enough MUs are already in the right format
diff --git a/swift/common/middleware/s3api/controllers/multi_upload.py b/swift/common/middleware/s3api/controllers/multi_upload.py
index 3ce12c5f7b..3f23f25a1c 100644
--- a/swift/common/middleware/s3api/controllers/multi_upload.py
+++ b/swift/common/middleware/s3api/controllers/multi_upload.py
@@ -397,7 +397,7 @@ class UploadsController(Controller):
             SubElement(owner_elem, 'DisplayName').text = req.user_id
             SubElement(upload_elem, 'StorageClass').text = 'STANDARD'
             SubElement(upload_elem, 'Initiated').text = \
-                u['last_modified'][:-3] + 'Z'
+                S3Timestamp.from_isoformat(u['last_modified']).s3xmlformat
 
         for p in prefixes:
             elem = SubElement(result_elem, 'CommonPrefixes')
@@ -582,7 +582,7 @@ class UploadController(Controller):
             part_elem = SubElement(result_elem, 'Part')
             SubElement(part_elem, 'PartNumber').text = i['name'].split('/')[-1]
             SubElement(part_elem, 'LastModified').text = \
-                i['last_modified'][:-3] + 'Z'
+                S3Timestamp.from_isoformat(i['last_modified']).s3xmlformat
             SubElement(part_elem, 'ETag').text = '"%s"' % i['hash']
             SubElement(part_elem, 'Size').text = str(i['bytes'])
 
diff --git a/swift/common/middleware/s3api/utils.py b/swift/common/middleware/s3api/utils.py
index 4c8a4fd670..40ff9388f6 100644
--- a/swift/common/middleware/s3api/utils.py
+++ b/swift/common/middleware/s3api/utils.py
@@ -15,6 +15,7 @@
 
 import base64
 import calendar
+import datetime
 import email.utils
 import re
 import six
@@ -108,9 +109,19 @@ def validate_bucket_name(name, dns_compliant_bucket_names):
 
 
 class S3Timestamp(utils.Timestamp):
+    S3_XML_FORMAT = "%Y-%m-%dT%H:%M:%S.000Z"
+
     @property
     def s3xmlformat(self):
-        return self.isoformat[:-7] + '.000Z'
+        dt = datetime.datetime.utcfromtimestamp(self.ceil())
+        return dt.strftime(self.S3_XML_FORMAT)
+
+    @classmethod
+    def from_s3xmlformat(cls, date_string):
+        dt = datetime.datetime.strptime(date_string, cls.S3_XML_FORMAT)
+        dt = dt.replace(tzinfo=utils.UTC)
+        seconds = calendar.timegm(dt.timetuple())
+        return cls(seconds)
 
     @property
     def amz_date_format(self):
diff --git a/swift/common/utils.py b/swift/common/utils.py
index 9dc8602015..b658d219a6 100644
--- a/swift/common/utils.py
+++ b/swift/common/utils.py
@@ -1324,6 +1324,15 @@ class Timestamp(object):
 
     @property
     def isoformat(self):
+        """
+        Get an isoformat string representation of the 'normal' part of the
+        Timestamp with microsecond precision and no trailing timezone, for
+        example:
+
+            1970-01-01T00:00:00.000000
+
+        :return: an isoformat string
+        """
         t = float(self.normal)
         if six.PY3:
             # On Python 3, round manually using ROUND_HALF_EVEN rounding
@@ -1350,6 +1359,21 @@ class Timestamp(object):
             isoformat += ".000000"
         return isoformat
 
+    @classmethod
+    def from_isoformat(cls, date_string):
+        """
+        Parse an isoformat string representation of time to a Timestamp object.
+
+        :param date_string: a string formatted as per an Timestamp.isoformat
+            property.
+        :return: an instance of  this class.
+        """
+        start = datetime.datetime.strptime(date_string, "%Y-%m-%dT%H:%M:%S.%f")
+        delta = start - EPOCH
+        # This calculation is based on Python 2.7's Modules/datetimemodule.c,
+        # function delta_to_microseconds(), but written in Python.
+        return cls(delta.total_seconds())
+
     def ceil(self):
         """
         Return the 'normal' part of the timestamp rounded up to the nearest
@@ -1506,13 +1530,7 @@ def last_modified_date_to_timestamp(last_modified_date_str):
     Convert a last modified date (like you'd get from a container listing,
     e.g. 2014-02-28T23:22:36.698390) to a float.
     """
-    start = datetime.datetime.strptime(last_modified_date_str,
-                                       '%Y-%m-%dT%H:%M:%S.%f')
-    delta = start - EPOCH
-
-    # This calculation is based on Python 2.7's Modules/datetimemodule.c,
-    # function delta_to_microseconds(), but written in Python.
-    return Timestamp(delta.total_seconds())
+    return Timestamp.from_isoformat(last_modified_date_str)
 
 
 def normalize_delete_at_timestamp(timestamp, high_precision=False):
diff --git a/test/functional/s3api/test_multi_upload.py b/test/functional/s3api/test_multi_upload.py
index 3ac8d668d8..1ff0b5e8b8 100644
--- a/test/functional/s3api/test_multi_upload.py
+++ b/test/functional/s3api/test_multi_upload.py
@@ -29,7 +29,8 @@ from six.moves import urllib, zip, zip_longest
 import test.functional as tf
 from swift.common.middleware.s3api.etree import fromstring, tostring, \
     Element, SubElement
-from swift.common.middleware.s3api.utils import MULTIUPLOAD_SUFFIX, mktime
+from swift.common.middleware.s3api.utils import MULTIUPLOAD_SUFFIX, mktime, \
+    S3Timestamp
 from swift.common.utils import md5
 
 from test.functional.s3api import S3ApiBase
@@ -213,7 +214,8 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertEqual(headers['content-type'], 'text/html; charset=UTF-8')
         self.assertTrue('content-length' in headers)
         self.assertEqual(headers['content-length'], '0')
-        expected_parts_list = [(headers['etag'], mktime(headers['date']))]
+        expected_parts_list = [(headers['etag'],
+                                mktime(headers['last-modified']))]
 
         # Upload Part Copy
         key, upload_id = uploads[1]
@@ -242,8 +244,8 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertTrue('etag' not in headers)
         elem = fromstring(body, 'CopyPartResult')
 
-        last_modified = elem.find('LastModified').text
-        self.assertTrue(last_modified is not None)
+        copy_resp_last_modified = elem.find('LastModified').text
+        self.assertIsNotNone(copy_resp_last_modified)
 
         self.assertEqual(resp_etag, etag)
 
@@ -256,15 +258,10 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertEqual(200, status)
         elem = fromstring(body, 'ListPartsResult')
 
-        # FIXME: COPY result drops milli/microseconds but GET doesn't
-        last_modified_gets = [p.find('LastModified').text
-                              for p in elem.iterfind('Part')]
-        self.assertEqual(
-            last_modified_gets[0].rsplit('.', 1)[0],
-            last_modified.rsplit('.', 1)[0],
-            '%r != %r' % (last_modified_gets[0], last_modified))
-        # There should be *exactly* two parts in the result
-        self.assertEqual(1, len(last_modified_gets))
+        listing_last_modified = [p.find('LastModified').text
+                                 for p in elem.iterfind('Part')]
+        # There should be *exactly* one parts in the result
+        self.assertEqual(listing_last_modified, [copy_resp_last_modified])
 
         # List Parts
         key, upload_id = uploads[0]
@@ -299,15 +296,10 @@ class TestS3ApiMultiUpload(S3ApiBase):
         for (expected_etag, expected_date), p in \
                 zip(expected_parts_list, elem.findall('Part')):
             last_modified = p.find('LastModified').text
-            self.assertTrue(last_modified is not None)
-            # TODO: sanity check
-            #       (kota_) How do we check the sanity?
-            #       the last-modified header drops milli-seconds info
-            #       by the constraint of the format.
-            #       For now, we can do either the format check or round check
-            # last_modified_from_xml = mktime(last_modified)
-            # self.assertEqual(expected_date,
-            #                   last_modified_from_xml)
+            self.assertIsNotNone(last_modified)
+            last_modified_from_xml = S3Timestamp.from_s3xmlformat(
+                last_modified)
+            self.assertEqual(expected_date, float(last_modified_from_xml))
             self.assertEqual(expected_etag, p.find('ETag').text)
             self.assertEqual(self.min_segment_size, int(p.find('Size').text))
             etags.append(p.find('ETag').text)
@@ -496,7 +488,7 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertIsNotNone(o.find('LastModified').text)
         self.assertRegex(
             o.find('LastModified').text,
-            r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$')
+            r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.000Z$')
         self.assertEqual(o.find('ETag').text, exp_etag)
         self.assertEqual(o.find('Size').text, str(exp_size))
         self.assertIsNotNone(o.find('StorageClass').text)
@@ -932,8 +924,8 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertTrue('etag' not in headers)
         elem = fromstring(body, 'CopyPartResult')
 
-        last_modified = elem.find('LastModified').text
-        self.assertTrue(last_modified is not None)
+        copy_resp_last_modified = elem.find('LastModified').text
+        self.assertIsNotNone(copy_resp_last_modified)
 
         self.assertEqual(resp_etag, etag)
 
@@ -945,16 +937,10 @@ class TestS3ApiMultiUpload(S3ApiBase):
 
         elem = fromstring(body, 'ListPartsResult')
 
-        # FIXME: COPY result drops milli/microseconds but GET doesn't
-        last_modified_gets = [p.find('LastModified').text
-                              for p in elem.iterfind('Part')]
-        self.assertEqual(
-            last_modified_gets[0].rsplit('.', 1)[0],
-            last_modified.rsplit('.', 1)[0],
-            '%r != %r' % (last_modified_gets[0], last_modified))
-
+        listing_last_modified = [p.find('LastModified').text
+                                 for p in elem.iterfind('Part')]
         # There should be *exactly* one parts in the result
-        self.assertEqual(1, len(last_modified_gets))
+        self.assertEqual(listing_last_modified, [copy_resp_last_modified])
 
         # Abort Multipart Upload
         key, upload_id = uploads[0]
@@ -1044,8 +1030,8 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertTrue('etag' not in headers)
         elem = fromstring(body, 'CopyPartResult')
 
-        last_modifieds = [elem.find('LastModified').text]
-        self.assertTrue(last_modifieds[0] is not None)
+        copy_resp_last_modifieds = [elem.find('LastModified').text]
+        self.assertTrue(copy_resp_last_modifieds[0] is not None)
 
         self.assertEqual(resp_etag, etags[0])
 
@@ -1062,8 +1048,8 @@ class TestS3ApiMultiUpload(S3ApiBase):
         self.assertTrue('etag' not in headers)
         elem = fromstring(body, 'CopyPartResult')
 
-        last_modifieds.append(elem.find('LastModified').text)
-        self.assertTrue(last_modifieds[1] is not None)
+        copy_resp_last_modifieds.append(elem.find('LastModified').text)
+        self.assertTrue(copy_resp_last_modifieds[1] is not None)
 
         self.assertEqual(resp_etag, etags[1])
 
@@ -1075,15 +1061,9 @@ class TestS3ApiMultiUpload(S3ApiBase):
 
         elem = fromstring(body, 'ListPartsResult')
 
-        # FIXME: COPY result drops milli/microseconds but GET doesn't
-        last_modified_gets = [p.find('LastModified').text
-                              for p in elem.iterfind('Part')]
-        self.assertEqual(
-            [lm.rsplit('.', 1)[0] for lm in last_modified_gets],
-            [lm.rsplit('.', 1)[0] for lm in last_modifieds])
-
-        # There should be *exactly* two parts in the result
-        self.assertEqual(2, len(last_modified_gets))
+        listing_last_modified = [p.find('LastModified').text
+                                 for p in elem.iterfind('Part')]
+        self.assertEqual(listing_last_modified, copy_resp_last_modifieds)
 
         # Abort Multipart Upload
         key, upload_id = uploads[0]
diff --git a/test/functional/s3api/test_object.py b/test/functional/s3api/test_object.py
index f8245318ef..5c0d847533 100644
--- a/test/functional/s3api/test_object.py
+++ b/test/functional/s3api/test_object.py
@@ -22,6 +22,7 @@ import boto
 # pylint: disable-msg=E0611,F0401
 from distutils.version import StrictVersion
 
+import calendar
 import email.parser
 from email.utils import formatdate, parsedate
 from time import mktime
@@ -30,6 +31,7 @@ import six
 import test.functional as tf
 
 from swift.common.middleware.s3api.etree import fromstring
+from swift.common.middleware.s3api.utils import S3Timestamp
 from swift.common.utils import md5, quote
 
 from test.functional.s3api import S3ApiBase
@@ -98,21 +100,32 @@ class TestS3ApiObject(S3ApiBase):
 
         elem = fromstring(body, 'CopyObjectResult')
         self.assertTrue(elem.find('LastModified').text is not None)
-        last_modified_xml = elem.find('LastModified').text
+        copy_resp_last_modified_xml = elem.find('LastModified').text
         self.assertTrue(elem.find('ETag').text is not None)
         self.assertEqual(etag, elem.find('ETag').text.strip('"'))
         self._assertObjectEtag(dst_bucket, dst_obj, etag)
 
-        # Check timestamp on Copy:
+        # Check timestamp on Copy in listing:
         status, headers, body = \
             self.conn.make_request('GET', dst_bucket)
         self.assertEqual(status, 200)
         elem = fromstring(body, 'ListBucketResult')
-
-        # FIXME: COPY result drops milli/microseconds but GET doesn't
         self.assertEqual(
-            elem.find('Contents').find("LastModified").text.rsplit('.', 1)[0],
-            last_modified_xml.rsplit('.', 1)[0])
+            elem.find('Contents').find("LastModified").text,
+            copy_resp_last_modified_xml)
+
+        # GET Object copy
+        status, headers, body = \
+            self.conn.make_request('GET', dst_bucket, dst_obj)
+        self.assertEqual(status, 200)
+
+        self.assertCommonResponseHeaders(headers, etag)
+        self.assertTrue(headers['last-modified'] is not None)
+        self.assertEqual(
+            float(S3Timestamp.from_s3xmlformat(copy_resp_last_modified_xml)),
+            calendar.timegm(parsedate(headers['last-modified'])))
+        self.assertTrue(headers['content-type'] is not None)
+        self.assertEqual(headers['content-length'], str(len(content)))
 
         # GET Object
         status, headers, body = \
@@ -770,6 +783,26 @@ class TestS3ApiObject(S3ApiBase):
         self.assertEqual(status, 200)
         self.assertCommonResponseHeaders(headers)
 
+        # check we can use the last modified time from the listing...
+        status, headers, body = \
+            self.conn.make_request('GET', self.bucket)
+        elem = fromstring(body, 'ListBucketResult')
+        last_modified = elem.find('./Contents/LastModified').text
+        listing_datetime = S3Timestamp.from_s3xmlformat(last_modified)
+        headers = \
+            {'If-Unmodified-Since': formatdate(listing_datetime)}
+        status, headers, body = \
+            self.conn.make_request('GET', self.bucket, obj, headers=headers)
+        self.assertEqual(status, 200)
+        self.assertCommonResponseHeaders(headers)
+
+        headers = \
+            {'If-Modified-Since': formatdate(listing_datetime)}
+        status, headers, body = \
+            self.conn.make_request('GET', self.bucket, obj, headers=headers)
+        self.assertEqual(status, 304)
+        self.assertCommonResponseHeaders(headers)
+
     def test_get_object_if_match(self):
         obj = 'object'
         self.conn.make_request('PUT', self.bucket, obj)
diff --git a/test/functional/s3api/test_presigned.py b/test/functional/s3api/test_presigned.py
index a06206b8b8..4ee115660a 100644
--- a/test/functional/s3api/test_presigned.py
+++ b/test/functional/s3api/test_presigned.py
@@ -92,7 +92,7 @@ class TestS3ApiPresignedUrls(S3ApiBase):
             self.assertIsNotNone(o.find('LastModified').text)
             self.assertRegex(
                 o.find('LastModified').text,
-                r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$')
+                r'^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.000Z$')
             self.assertIsNotNone(o.find('ETag').text)
             self.assertEqual(o.find('Size').text, '0')
             self.assertIsNotNone(o.find('StorageClass').text is not None)
diff --git a/test/unit/__init__.py b/test/unit/__init__.py
index 40d6069337..f7f4b22fe5 100644
--- a/test/unit/__init__.py
+++ b/test/unit/__init__.py
@@ -1042,9 +1042,9 @@ def make_timestamp_iter(offset=0):
 
 
 @contextmanager
-def mock_timestamp_now(now=None):
+def mock_timestamp_now(now=None, klass=Timestamp):
     if now is None:
-        now = Timestamp.now()
+        now = klass.now()
     with mocklib.patch('swift.common.utils.Timestamp.now',
                        classmethod(lambda c: now)):
         yield now
diff --git a/test/unit/common/middleware/s3api/test_bucket.py b/test/unit/common/middleware/s3api/test_bucket.py
index 6b6b1dc73e..2eae7faa98 100644
--- a/test/unit/common/middleware/s3api/test_bucket.py
+++ b/test/unit/common/middleware/s3api/test_bucket.py
@@ -201,7 +201,7 @@ class TestS3ApiBucket(S3ApiTestCase):
         items = []
         for o in objects:
             items.append((o.find('./Key').text, o.find('./ETag').text))
-            self.assertEqual('2011-01-05T02:19:14.275Z',
+            self.assertEqual('2011-01-05T02:19:15.000Z',
                              o.find('./LastModified').text)
         expected = [
             (i[0].encode('utf-8') if six.PY2 else i[0],
@@ -211,6 +211,37 @@ class TestS3ApiBucket(S3ApiTestCase):
         ]
         self.assertEqual(items, expected)
 
+    def test_bucket_GET_last_modified_rounding(self):
+        objects_list = [
+            {'name': 'a', 'last_modified': '2011-01-05T02:19:59.275290',
+             'content_type': 'application/octet-stream',
+             'hash': 'ahash', 'bytes': '12345'},
+            {'name': 'b', 'last_modified': '2011-01-05T02:19:59.000000',
+             'content_type': 'application/octet-stream',
+             'hash': 'ahash', 'bytes': '12345'},
+        ]
+        self.swift.register(
+            'GET', '/v1/AUTH_test/junk',
+            swob.HTTPOk, {'Content-Type': 'application/json'},
+            json.dumps(objects_list))
+        req = Request.blank('/junk',
+                            environ={'REQUEST_METHOD': 'GET'},
+                            headers={'Authorization': 'AWS test:tester:hmac',
+                                     'Date': self.get_date_header()})
+        status, headers, body = self.call_s3api(req)
+        self.assertEqual(status.split()[0], '200')
+
+        elem = fromstring(body, 'ListBucketResult')
+        name = elem.find('./Name').text
+        self.assertEqual(name, 'junk')
+        objects = elem.iterchildren('Contents')
+        actual = [(obj.find('./Key').text, obj.find('./LastModified').text)
+                  for obj in objects]
+        self.assertEqual(
+            [('a', '2011-01-05T02:20:00.000Z'),
+             ('b', '2011-01-05T02:19:59.000Z')],
+            actual)
+
     def test_bucket_GET_url_encoded(self):
         bucket_name = 'junk'
         req = Request.blank('/%s?encoding-type=url' % bucket_name,
@@ -229,7 +260,7 @@ class TestS3ApiBucket(S3ApiTestCase):
         items = []
         for o in objects:
             items.append((o.find('./Key').text, o.find('./ETag').text))
-            self.assertEqual('2011-01-05T02:19:14.275Z',
+            self.assertEqual('2011-01-05T02:19:15.000Z',
                              o.find('./LastModified').text)
 
         self.assertEqual(items, [
@@ -673,9 +704,9 @@ class TestS3ApiBucket(S3ApiTestCase):
         self.assertEqual([v.find('./VersionId').text for v in versions],
                          ['null' for v in objects])
         # Last modified in self.objects is 2011-01-05T02:19:14.275290 but
-        # the returned value is 2011-01-05T02:19:14.275Z
+        # the returned value is rounded up to 2011-01-05T02:19:15Z
         self.assertEqual([v.find('./LastModified').text for v in versions],
-                         [v[1][:-3] + 'Z' for v in objects])
+                         ['2011-01-05T02:19:15.000Z'] * len(objects))
         self.assertEqual([v.find('./ETag').text for v in versions],
                          [PFS_ETAG if v[0] == 'pfs-obj' else
                           '"0-N"' if v[0] == 'slo' else '"0"'
diff --git a/test/unit/common/middleware/s3api/test_multi_upload.py b/test/unit/common/middleware/s3api/test_multi_upload.py
index 63ab8e81fb..4eff8015a1 100644
--- a/test/unit/common/middleware/s3api/test_multi_upload.py
+++ b/test/unit/common/middleware/s3api/test_multi_upload.py
@@ -51,29 +51,41 @@ XML = '<CompleteMultipartUpload>' \
     '</CompleteMultipartUpload>'
 
 OBJECTS_TEMPLATE = \
-    (('object/X/1', '2014-05-07T19:47:51.592270', '0123456789abcdef', 100),
-     ('object/X/2', '2014-05-07T19:47:52.592270', 'fedcba9876543210', 200))
+    (('object/X/1', '2014-05-07T19:47:51.592270', '0123456789abcdef', 100,
+      '2014-05-07T19:47:52.000Z'),
+     ('object/X/2', '2014-05-07T19:47:52.592270', 'fedcba9876543210', 200,
+      '2014-05-07T19:47:53.000Z'))
 
 MULTIPARTS_TEMPLATE = \
-    (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1),
-     ('object/X/1', '2014-05-07T19:47:51.592270', '0123456789abcdef', 11),
-     ('object/X/2', '2014-05-07T19:47:52.592270', 'fedcba9876543210', 21),
-     ('object/Y', '2014-05-07T19:47:53.592270', 'HASH', 2),
-     ('object/Y/1', '2014-05-07T19:47:54.592270', '0123456789abcdef', 12),
-     ('object/Y/2', '2014-05-07T19:47:55.592270', 'fedcba9876543210', 22),
-     ('object/Z', '2014-05-07T19:47:56.592270', 'HASH', 3),
-     ('object/Z/1', '2014-05-07T19:47:57.592270', '0123456789abcdef', 13),
-     ('object/Z/2', '2014-05-07T19:47:58.592270', 'fedcba9876543210', 23),
-     ('subdir/object/Z', '2014-05-07T19:47:58.592270', 'HASH', 4),
+    (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1,
+      '2014-05-07T19:47:51.000Z'),
+     ('object/X/1', '2014-05-07T19:47:51.592270', '0123456789abcdef', 11,
+      '2014-05-07T19:47:52.000Z'),
+     ('object/X/2', '2014-05-07T19:47:52.592270', 'fedcba9876543210', 21,
+      '2014-05-07T19:47:53.000Z'),
+     ('object/Y', '2014-05-07T19:47:53.592270', 'HASH', 2,
+      '2014-05-07T19:47:54.000Z'),
+     ('object/Y/1', '2014-05-07T19:47:54.592270', '0123456789abcdef', 12,
+      '2014-05-07T19:47:55.000Z'),
+     ('object/Y/2', '2014-05-07T19:47:55.592270', 'fedcba9876543210', 22,
+      '2014-05-07T19:47:56.000Z'),
+     ('object/Z', '2014-05-07T19:47:56.592270', 'HASH', 3,
+      '2014-05-07T19:47:57.000Z'),
+     ('object/Z/1', '2014-05-07T19:47:57.592270', '0123456789abcdef', 13,
+      '2014-05-07T19:47:58.000Z'),
+     ('object/Z/2', '2014-05-07T19:47:58.592270', 'fedcba9876543210', 23,
+      '2014-05-07T19:47:59.000Z'),
+     ('subdir/object/Z', '2014-05-07T19:47:58.592270', 'HASH', 4,
+      '2014-05-07T19:47:59.000Z'),
      ('subdir/object/Z/1', '2014-05-07T19:47:58.592270', '0123456789abcdef',
-      41),
+      41, '2014-05-07T19:47:59.000Z'),
      ('subdir/object/Z/2', '2014-05-07T19:47:58.592270', 'fedcba9876543210',
-      41),
+      41, '2014-05-07T19:47:59.000Z'),
      # NB: wsgi strings
      ('subdir/object/completed\xe2\x98\x83/W/1', '2014-05-07T19:47:58.592270',
-      '0123456789abcdef', 41),
+      '0123456789abcdef', 41, '2014-05-07T19:47:59.000Z'),
      ('subdir/object/completed\xe2\x98\x83/W/2', '2014-05-07T19:47:58.592270',
-      'fedcba9876543210', 41))
+      'fedcba9876543210', 41, '2014-05-07T19:47:59'))
 
 S3_ETAG = '"%s-2"' % md5(binascii.a2b_hex(
     '0123456789abcdef0123456789abcdef'
@@ -285,7 +297,7 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
         self.assertEqual(elem.find('MaxUploads').text, '1000')
         self.assertEqual(elem.find('IsTruncated').text, 'false')
         self.assertEqual(len(elem.findall('Upload')), len(uploads))
-        expected_uploads = [(upload[0], '2014-05-07T19:47:50.592Z')
+        expected_uploads = [(upload[0], '2014-05-07T19:47:51.000Z')
                             for upload in uploads]
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
@@ -310,7 +322,7 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
         self.assertEqual(elem.find('MaxUploads').text, '1000')
         self.assertEqual(elem.find('IsTruncated').text, 'false')
         self.assertEqual(len(elem.findall('Upload')), 4)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in MULTIPARTS_TEMPLATE]
+        objects = [(o[0], o[4]) for o in MULTIPARTS_TEMPLATE]
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
             initiated = u.find('Initiated').text
@@ -417,9 +429,12 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
     def test_bucket_multipart_uploads_GET_with_id_and_key_marker(self):
         query = 'upload-id-marker=Y&key-marker=object'
         multiparts = \
-            (('object/Y', '2014-05-07T19:47:53.592270', 'HASH', 2),
-             ('object/Y/1', '2014-05-07T19:47:54.592270', 'HASH', 12),
-             ('object/Y/2', '2014-05-07T19:47:55.592270', 'HASH', 22))
+            (('object/Y', '2014-05-07T19:47:53.592270', 'HASH', 2,
+              '2014-05-07T19:47:54.000Z'),
+             ('object/Y/1', '2014-05-07T19:47:54.592270', 'HASH', 12,
+              '2014-05-07T19:47:55.000Z'),
+             ('object/Y/2', '2014-05-07T19:47:55.592270', 'HASH', 22,
+              '2014-05-07T19:47:56.000Z'))
 
         status, headers, body = \
             self._test_bucket_multipart_uploads_GET(query, multiparts)
@@ -427,7 +442,7 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
         self.assertEqual(elem.find('KeyMarker').text, 'object')
         self.assertEqual(elem.find('UploadIdMarker').text, 'Y')
         self.assertEqual(len(elem.findall('Upload')), 1)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in multiparts]
+        objects = [(o[0], o[4]) for o in multiparts]
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
             initiated = u.find('Initiated').text
@@ -447,12 +462,18 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
     def test_bucket_multipart_uploads_GET_with_key_marker(self):
         query = 'key-marker=object'
         multiparts = \
-            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1),
-             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11),
-             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21),
-             ('object/Y', '2014-05-07T19:47:53.592270', 'HASH', 2),
-             ('object/Y/1', '2014-05-07T19:47:54.592270', 'HASH', 12),
-             ('object/Y/2', '2014-05-07T19:47:55.592270', 'HASH', 22))
+            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1,
+              '2014-05-07T19:47:51.000Z'),
+             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11,
+              '2014-05-07T19:47:52.000Z'),
+             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21,
+              '2014-05-07T19:47:53.000Z'),
+             ('object/Y', '2014-05-07T19:47:53.592270', 'HASH', 2,
+              '2014-05-07T19:47:54.000Z'),
+             ('object/Y/1', '2014-05-07T19:47:54.592270', 'HASH', 12,
+              '2014-05-07T19:47:55.000Z'),
+             ('object/Y/2', '2014-05-07T19:47:55.592270', 'HASH', 22,
+              '2014-05-07T19:47:56.000Z'))
         status, headers, body = \
             self._test_bucket_multipart_uploads_GET(query, multiparts)
         elem = fromstring(body, 'ListMultipartUploadsResult')
@@ -460,11 +481,11 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
         self.assertEqual(elem.find('NextKeyMarker').text, 'object')
         self.assertEqual(elem.find('NextUploadIdMarker').text, 'Y')
         self.assertEqual(len(elem.findall('Upload')), 2)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in multiparts]
+        objects = [(o[0], o[4]) for o in multiparts]
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
             initiated = u.find('Initiated').text
-            self.assertTrue((name, initiated) in objects)
+            self.assertIn((name, initiated), objects)
         self.assertEqual(status.split()[0], '200')
 
         _, path, _ = self.swift.calls_with_headers[-1]
@@ -480,14 +501,17 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
     def test_bucket_multipart_uploads_GET_with_prefix(self):
         query = 'prefix=X'
         multiparts = \
-            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1),
-             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11),
-             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21))
+            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1,
+              '2014-05-07T19:47:51.000Z'),
+             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11,
+              '2014-05-07T19:47:52.000Z'),
+             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21,
+              '2014-05-07T19:47:53.000Z'))
         status, headers, body = \
             self._test_bucket_multipart_uploads_GET(query, multiparts)
         elem = fromstring(body, 'ListMultipartUploadsResult')
         self.assertEqual(len(elem.findall('Upload')), 1)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in multiparts]
+        objects = [(o[0], o[4]) for o in multiparts]
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
             initiated = u.find('Initiated').text
@@ -507,38 +531,56 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
     def test_bucket_multipart_uploads_GET_with_delimiter(self):
         query = 'delimiter=/'
         multiparts = \
-            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1),
-             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11),
-             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21),
-             ('object/Y', '2014-05-07T19:47:50.592270', 'HASH', 2),
-             ('object/Y/1', '2014-05-07T19:47:51.592270', 'HASH', 21),
-             ('object/Y/2', '2014-05-07T19:47:52.592270', 'HASH', 22),
-             ('object/Z', '2014-05-07T19:47:50.592270', 'HASH', 3),
-             ('object/Z/1', '2014-05-07T19:47:51.592270', 'HASH', 31),
-             ('object/Z/2', '2014-05-07T19:47:52.592270', 'HASH', 32),
-             ('subdir/object/X', '2014-05-07T19:47:50.592270', 'HASH', 4),
-             ('subdir/object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 41),
-             ('subdir/object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 42),
-             ('subdir/object/Y', '2014-05-07T19:47:50.592270', 'HASH', 5),
-             ('subdir/object/Y/1', '2014-05-07T19:47:51.592270', 'HASH', 51),
-             ('subdir/object/Y/2', '2014-05-07T19:47:52.592270', 'HASH', 52),
-             ('subdir2/object/Z', '2014-05-07T19:47:50.592270', 'HASH', 6),
-             ('subdir2/object/Z/1', '2014-05-07T19:47:51.592270', 'HASH', 61),
-             ('subdir2/object/Z/2', '2014-05-07T19:47:52.592270', 'HASH', 62))
+            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1,
+              '2014-05-07T19:47:51.000Z'),
+             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11,
+              '2014-05-07T19:47:52.000Z'),
+             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21,
+              '2014-05-07T19:47:53.000Z'),
+             ('object/Y', '2014-05-07T19:47:50.592270', 'HASH', 2,
+              '2014-05-07T19:47:51.000Z'),
+             ('object/Y/1', '2014-05-07T19:47:51.592270', 'HASH', 21,
+              '2014-05-07T19:47:52.000Z'),
+             ('object/Y/2', '2014-05-07T19:47:52.592270', 'HASH', 22,
+              '2014-05-07T19:47:53.000Z'),
+             ('object/Z', '2014-05-07T19:47:50.592270', 'HASH', 3,
+              '2014-05-07T19:47:51.000Z'),
+             ('object/Z/1', '2014-05-07T19:47:51.592270', 'HASH', 31,
+              '2014-05-07T19:47:52.000Z'),
+             ('object/Z/2', '2014-05-07T19:47:52.592270', 'HASH', 32,
+              '2014-05-07T19:47:53.000Z'),
+             ('subdir/object/X', '2014-05-07T19:47:50.592270', 'HASH', 4,
+              '2014-05-07T19:47:51.000Z'),
+             ('subdir/object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 41,
+              '2014-05-07T19:47:52.000Z'),
+             ('subdir/object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 42,
+              '2014-05-07T19:47:53.000Z'),
+             ('subdir/object/Y', '2014-05-07T19:47:50.592270', 'HASH', 5,
+              '2014-05-07T19:47:51.000Z'),
+             ('subdir/object/Y/1', '2014-05-07T19:47:51.592270', 'HASH', 51,
+              '2014-05-07T19:47:52.000Z'),
+             ('subdir/object/Y/2', '2014-05-07T19:47:52.592270', 'HASH', 52,
+              '2014-05-07T19:47:53.000Z'),
+             ('subdir2/object/Z', '2014-05-07T19:47:50.592270', 'HASH', 6,
+              '2014-05-07T19:47:51.000Z'),
+             ('subdir2/object/Z/1', '2014-05-07T19:47:51.592270', 'HASH', 61,
+              '2014-05-07T19:47:52.000Z'),
+             ('subdir2/object/Z/2', '2014-05-07T19:47:52.592270', 'HASH', 62,
+              '2014-05-07T19:47:53.000Z'))
 
         status, headers, body = \
             self._test_bucket_multipart_uploads_GET(query, multiparts)
         elem = fromstring(body, 'ListMultipartUploadsResult')
         self.assertEqual(len(elem.findall('Upload')), 3)
         self.assertEqual(len(elem.findall('CommonPrefixes')), 2)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in multiparts
+        objects = [(o[0], o[4]) for o in multiparts
                    if o[0].startswith('o')]
         prefixes = set([o[0].split('/')[0] + '/' for o in multiparts
                        if o[0].startswith('s')])
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
             initiated = u.find('Initiated').text
-            self.assertTrue((name, initiated) in objects)
+            self.assertIn((name, initiated), objects)
         for p in elem.findall('CommonPrefixes'):
             prefix = p.find('Prefix').text
             self.assertTrue(prefix in prefixes)
@@ -557,31 +599,43 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
     def test_bucket_multipart_uploads_GET_with_multi_chars_delimiter(self):
         query = 'delimiter=subdir'
         multiparts = \
-            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1),
-             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11),
-             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21),
+            (('object/X', '2014-05-07T19:47:50.592270', 'HASH', 1,
+              '2014-05-07T19:47:51.000Z'),
+             ('object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 11,
+              '2014-05-07T19:47:52.000Z'),
+             ('object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 21,
+              '2014-05-07T19:47:53.000Z'),
              ('dir/subdir/object/X', '2014-05-07T19:47:50.592270',
-              'HASH', 3),
+              'HASH', 3, '2014-05-07T19:47:51.000Z'),
              ('dir/subdir/object/X/1', '2014-05-07T19:47:51.592270',
-              'HASH', 31),
+              'HASH', 31, '2014-05-07T19:47:52.000Z'),
              ('dir/subdir/object/X/2', '2014-05-07T19:47:52.592270',
-              'HASH', 32),
-             ('subdir/object/X', '2014-05-07T19:47:50.592270', 'HASH', 4),
-             ('subdir/object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 41),
-             ('subdir/object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 42),
-             ('subdir/object/Y', '2014-05-07T19:47:50.592270', 'HASH', 5),
-             ('subdir/object/Y/1', '2014-05-07T19:47:51.592270', 'HASH', 51),
-             ('subdir/object/Y/2', '2014-05-07T19:47:52.592270', 'HASH', 52),
-             ('subdir2/object/Z', '2014-05-07T19:47:50.592270', 'HASH', 6),
-             ('subdir2/object/Z/1', '2014-05-07T19:47:51.592270', 'HASH', 61),
-             ('subdir2/object/Z/2', '2014-05-07T19:47:52.592270', 'HASH', 62))
+              'HASH', 32, '2014-05-07T19:47:53.000Z'),
+             ('subdir/object/X', '2014-05-07T19:47:50.592270', 'HASH', 4,
+              '2014-05-07T19:47:51.000Z'),
+             ('subdir/object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 41,
+              '2014-05-07T19:47:52.000Z'),
+             ('subdir/object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 42,
+              '2014-05-07T19:47:53.000Z'),
+             ('subdir/object/Y', '2014-05-07T19:47:50.592270', 'HASH', 5,
+              '2014-05-07T19:47:51.000Z'),
+             ('subdir/object/Y/1', '2014-05-07T19:47:51.592270', 'HASH', 51,
+              '2014-05-07T19:47:52.000Z'),
+             ('subdir/object/Y/2', '2014-05-07T19:47:52.592270', 'HASH', 52,
+              '2014-05-07T19:47:53.000Z'),
+             ('subdir2/object/Z', '2014-05-07T19:47:50.592270', 'HASH', 6,
+              '2014-05-07T19:47:51.000Z'),
+             ('subdir2/object/Z/1', '2014-05-07T19:47:51.592270', 'HASH', 61,
+              '2014-05-07T19:47:52.000Z'),
+             ('subdir2/object/Z/2', '2014-05-07T19:47:52.592270', 'HASH', 62,
+              '2014-05-07T19:47:53.000Z'))
 
         status, headers, body = \
             self._test_bucket_multipart_uploads_GET(query, multiparts)
         elem = fromstring(body, 'ListMultipartUploadsResult')
         self.assertEqual(len(elem.findall('Upload')), 1)
         self.assertEqual(len(elem.findall('CommonPrefixes')), 2)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in multiparts
+        objects = [(o[0], o[4]) for o in multiparts
                    if o[0].startswith('object')]
         prefixes = ('dir/subdir', 'subdir')
         for u in elem.findall('Upload'):
@@ -607,27 +661,30 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
         query = 'prefix=dir/&delimiter=/'
         multiparts = \
             (('dir/subdir/object/X', '2014-05-07T19:47:50.592270',
-              'HASH', 4),
+              'HASH', 4, '2014-05-07T19:47:51.000Z'),
              ('dir/subdir/object/X/1', '2014-05-07T19:47:51.592270',
-              'HASH', 41),
+              'HASH', 41, '2014-05-07T19:47:52.000Z'),
              ('dir/subdir/object/X/2', '2014-05-07T19:47:52.592270',
-              'HASH', 42),
-             ('dir/object/X', '2014-05-07T19:47:50.592270', 'HASH', 5),
-             ('dir/object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 51),
-             ('dir/object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 52))
+              'HASH', 42, '2014-05-07T19:47:53.000Z'),
+             ('dir/object/X', '2014-05-07T19:47:50.592270', 'HASH', 5,
+              '2014-05-07T19:47:51.000Z'),
+             ('dir/object/X/1', '2014-05-07T19:47:51.592270', 'HASH', 51,
+              '2014-05-07T19:47:52.000Z'),
+             ('dir/object/X/2', '2014-05-07T19:47:52.592270', 'HASH', 52,
+              '2014-05-07T19:47:53.000Z'))
 
         status, headers, body = \
             self._test_bucket_multipart_uploads_GET(query, multiparts)
         elem = fromstring(body, 'ListMultipartUploadsResult')
         self.assertEqual(len(elem.findall('Upload')), 1)
         self.assertEqual(len(elem.findall('CommonPrefixes')), 1)
-        objects = [(o[0], o[1][:-3] + 'Z') for o in multiparts
+        objects = [(o[0], o[4]) for o in multiparts
                    if o[0].startswith('dir/o')]
         prefixes = ['dir/subdir/']
         for u in elem.findall('Upload'):
             name = u.find('Key').text + '/' + u.find('UploadId').text
             initiated = u.find('Initiated').text
-            self.assertTrue((name, initiated) in objects)
+            self.assertIn((name, initiated), objects)
         for p in elem.findall('CommonPrefixes'):
             prefix = p.find('Prefix').text
             self.assertTrue(prefix in prefixes)
@@ -1838,6 +1895,9 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
              'hash': hex(i),
              'bytes': 100 * i}
             for i in range(1, 2000)]
+        ceil_last_modified = ['2014-05-07T19:%02d:%02d.000Z'
+                              % (47 if (i + 1) % 60 else 48, (i + 1) % 60)
+                              for i in range(1, 2000)]
         swift_sorted = sorted(swift_parts, key=lambda part: part['name'])
         self.swift.register('GET',
                             "%s?delimiter=/&format=json&marker=&"
@@ -1872,7 +1932,7 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
             s3_parts.append(partnum)
             self.assertEqual(
                 p.find('LastModified').text,
-                swift_parts[partnum - 1]['last_modified'][:-3] + 'Z')
+                ceil_last_modified[partnum - 1])
             self.assertEqual(p.find('ETag').text.strip(),
                              '"%s"' % swift_parts[partnum - 1]['hash'])
             self.assertEqual(p.find('Size').text,
@@ -1970,7 +2030,7 @@ class TestS3ApiMultiUpload(S3ApiTestCase):
         for p in elem.findall('Part'):
             partnum = int(p.find('PartNumber').text)
             self.assertEqual(p.find('LastModified').text,
-                             OBJECTS_TEMPLATE[partnum - 1][1][:-3] + 'Z')
+                             OBJECTS_TEMPLATE[partnum - 1][4])
             self.assertEqual(p.find('ETag').text,
                              '"%s"' % OBJECTS_TEMPLATE[partnum - 1][2])
             self.assertEqual(p.find('Size').text,
diff --git a/test/unit/common/middleware/s3api/test_obj.py b/test/unit/common/middleware/s3api/test_obj.py
index cd7c06d2dc..870bf7acf6 100644
--- a/test/unit/common/middleware/s3api/test_obj.py
+++ b/test/unit/common/middleware/s3api/test_obj.py
@@ -28,6 +28,7 @@ import json
 from swift.common import swob
 from swift.common.swob import Request
 from swift.common.middleware.proxy_logging import ProxyLoggingMiddleware
+from test.unit import mock_timestamp_now
 
 from test.unit.common.middleware.s3api import S3ApiTestCase
 from test.unit.common.middleware.s3api.test_s3_acl import s3acl
@@ -872,33 +873,29 @@ class TestS3ApiObj(S3ApiTestCase):
 
     @s3acl
     def test_object_PUT_copy_metadata_replace(self):
-        date_header = self.get_date_header()
-        timestamp = mktime(date_header)
-        allowed_last_modified = [S3Timestamp(timestamp).s3xmlformat]
-        status, headers, body = \
-            self._test_object_PUT_copy(
-                swob.HTTPOk,
-                {'X-Amz-Metadata-Directive': 'REPLACE',
-                 'X-Amz-Meta-Something': 'oh hai',
-                 'X-Amz-Meta-Unreadable-Prefix': '\x04w',
-                 'X-Amz-Meta-Unreadable-Suffix': 'h\x04',
-                 'X-Amz-Meta-Lots-Of-Unprintable': 5 * '\x04',
-                 'Cache-Control': 'hello',
-                 'content-disposition': 'how are you',
-                 'content-encoding': 'good and you',
-                 'content-language': 'great',
-                 'content-type': 'so',
-                 'expires': 'yeah',
-                 'x-robots-tag': 'bye'})
-        date_header = self.get_date_header()
-        timestamp = mktime(date_header)
-        allowed_last_modified.append(S3Timestamp(timestamp).s3xmlformat)
+        with mock_timestamp_now(klass=S3Timestamp) as now:
+            status, headers, body = \
+                self._test_object_PUT_copy(
+                    swob.HTTPOk,
+                    {'X-Amz-Metadata-Directive': 'REPLACE',
+                     'X-Amz-Meta-Something': 'oh hai',
+                     'X-Amz-Meta-Unreadable-Prefix': '\x04w',
+                     'X-Amz-Meta-Unreadable-Suffix': 'h\x04',
+                     'X-Amz-Meta-Lots-Of-Unprintable': 5 * '\x04',
+                     'Cache-Control': 'hello',
+                     'content-disposition': 'how are you',
+                     'content-encoding': 'good and you',
+                     'content-language': 'great',
+                     'content-type': 'so',
+                     'expires': 'yeah',
+                     'x-robots-tag': 'bye'})
 
         self.assertEqual(status.split()[0], '200')
         self.assertEqual(headers['Content-Type'], 'application/xml')
         self.assertIsNone(headers.get('etag'))
         elem = fromstring(body, 'CopyObjectResult')
-        self.assertIn(elem.find('LastModified').text, allowed_last_modified)
+        self.assertEqual(S3Timestamp(now.ceil()).s3xmlformat,
+                         elem.find('LastModified').text)
         self.assertEqual(elem.find('ETag').text, '"%s"' % self.etag)
 
         _, _, headers = self.swift.calls_with_headers[-1]
@@ -926,34 +923,30 @@ class TestS3ApiObj(S3ApiTestCase):
 
     @s3acl
     def test_object_PUT_copy_metadata_copy(self):
-        date_header = self.get_date_header()
-        timestamp = mktime(date_header)
-        allowed_last_modified = [S3Timestamp(timestamp).s3xmlformat]
-        status, headers, body = \
-            self._test_object_PUT_copy(
-                swob.HTTPOk,
-                {'X-Amz-Metadata-Directive': 'COPY',
-                 'X-Amz-Meta-Something': 'oh hai',
-                 'X-Amz-Meta-Unreadable-Prefix': '\x04w',
-                 'X-Amz-Meta-Unreadable-Suffix': 'h\x04',
-                 'X-Amz-Meta-Lots-Of-Unprintable': 5 * '\x04',
-                 'Cache-Control': 'hello',
-                 'content-disposition': 'how are you',
-                 'content-encoding': 'good and you',
-                 'content-language': 'great',
-                 'content-type': 'so',
-                 'expires': 'yeah',
-                 'x-robots-tag': 'bye'})
-        date_header = self.get_date_header()
-        timestamp = mktime(date_header)
-        allowed_last_modified.append(S3Timestamp(timestamp).s3xmlformat)
+        with mock_timestamp_now(klass=S3Timestamp) as now:
+            status, headers, body = \
+                self._test_object_PUT_copy(
+                    swob.HTTPOk,
+                    {'X-Amz-Metadata-Directive': 'COPY',
+                     'X-Amz-Meta-Something': 'oh hai',
+                     'X-Amz-Meta-Unreadable-Prefix': '\x04w',
+                     'X-Amz-Meta-Unreadable-Suffix': 'h\x04',
+                     'X-Amz-Meta-Lots-Of-Unprintable': 5 * '\x04',
+                     'Cache-Control': 'hello',
+                     'content-disposition': 'how are you',
+                     'content-encoding': 'good and you',
+                     'content-language': 'great',
+                     'content-type': 'so',
+                     'expires': 'yeah',
+                     'x-robots-tag': 'bye'})
 
         self.assertEqual(status.split()[0], '200')
         self.assertEqual(headers['Content-Type'], 'application/xml')
         self.assertIsNone(headers.get('etag'))
 
         elem = fromstring(body, 'CopyObjectResult')
-        self.assertIn(elem.find('LastModified').text, allowed_last_modified)
+        self.assertEqual(S3Timestamp(now.ceil()).s3xmlformat,
+                         elem.find('LastModified').text)
         self.assertEqual(elem.find('ETag').text, '"%s"' % self.etag)
 
         _, _, headers = self.swift.calls_with_headers[-1]
diff --git a/test/unit/common/middleware/s3api/test_utils.py b/test/unit/common/middleware/s3api/test_utils.py
index ad6fc119fa..9fc0854f52 100644
--- a/test/unit/common/middleware/s3api/test_utils.py
+++ b/test/unit/common/middleware/s3api/test_utils.py
@@ -81,21 +81,6 @@ class TestS3ApiUtils(unittest.TestCase):
         self.assertFalse(utils.validate_bucket_name('bucket.', False))
         self.assertFalse(utils.validate_bucket_name('a' * 256, False))
 
-    def test_s3timestamp(self):
-        expected = '1970-01-01T00:00:01.000Z'
-        # integer
-        ts = utils.S3Timestamp(1)
-        self.assertEqual(expected, ts.s3xmlformat)
-        # milliseconds unit should be floored
-        ts = utils.S3Timestamp(1.1)
-        self.assertEqual(expected, ts.s3xmlformat)
-        # float (microseconds) should be floored too
-        ts = utils.S3Timestamp(1.000001)
-        self.assertEqual(expected, ts.s3xmlformat)
-        # Bigger float (milliseconds) should be floored too
-        ts = utils.S3Timestamp(1.9)
-        self.assertEqual(expected, ts.s3xmlformat)
-
     def test_mktime(self):
         date_headers = [
             'Thu, 01 Jan 1970 00:00:00 -0000',
@@ -130,6 +115,48 @@ class TestS3ApiUtils(unittest.TestCase):
             time.tzset()
 
 
+class TestS3Timestamp(unittest.TestCase):
+    def test_s3xmlformat(self):
+        expected = '1970-01-01T00:00:01.000Z'
+        # integer
+        ts = utils.S3Timestamp(1)
+        self.assertEqual(expected, ts.s3xmlformat)
+        # milliseconds unit should be rounded up
+        expected = '1970-01-01T00:00:02.000Z'
+        ts = utils.S3Timestamp(1.1)
+        self.assertEqual(expected, ts.s3xmlformat)
+        # float (microseconds) should be floored too
+        ts = utils.S3Timestamp(1.000001)
+        self.assertEqual(expected, ts.s3xmlformat)
+        # Bigger float (milliseconds) should be floored too
+        ts = utils.S3Timestamp(1.9)
+        self.assertEqual(expected, ts.s3xmlformat)
+
+    def test_from_s3xmlformat(self):
+        ts = utils.S3Timestamp.from_s3xmlformat('2014-06-10T22:47:32.000Z')
+        self.assertIsInstance(ts, utils.S3Timestamp)
+        self.assertEqual(1402440452, float(ts))
+        self.assertEqual('2014-06-10T22:47:32.000000', ts.isoformat)
+
+        ts = utils.S3Timestamp.from_s3xmlformat('1970-01-01T00:00:00.000Z')
+        self.assertIsInstance(ts, utils.S3Timestamp)
+        self.assertEqual(0.0, float(ts))
+        self.assertEqual('1970-01-01T00:00:00.000000', ts.isoformat)
+
+        ts = utils.S3Timestamp(1402440452.0)
+        self.assertIsInstance(ts, utils.S3Timestamp)
+        ts1 = utils.S3Timestamp.from_s3xmlformat(ts.s3xmlformat)
+        self.assertIsInstance(ts1, utils.S3Timestamp)
+        self.assertEqual(ts, ts1)
+
+    def test_from_isoformat(self):
+        ts = utils.S3Timestamp.from_isoformat('2014-06-10T22:47:32.054580')
+        self.assertIsInstance(ts, utils.S3Timestamp)
+        self.assertEqual(1402440452.05458, float(ts))
+        self.assertEqual('2014-06-10T22:47:32.054580', ts.isoformat)
+        self.assertEqual('2014-06-10T22:47:33.000Z', ts.s3xmlformat)
+
+
 class TestConfig(unittest.TestCase):
 
     def _assert_defaults(self, conf):
diff --git a/test/unit/common/test_utils.py b/test/unit/common/test_utils.py
index 06e84c3a58..2afc26decb 100644
--- a/test/unit/common/test_utils.py
+++ b/test/unit/common/test_utils.py
@@ -305,6 +305,21 @@ class TestTimestamp(unittest.TestCase):
         for value in test_values:
             self.assertEqual(utils.Timestamp(value).isoformat, expected)
 
+    def test_from_isoformat(self):
+        ts = utils.Timestamp.from_isoformat('2014-06-10T22:47:32.054580')
+        self.assertIsInstance(ts, utils.Timestamp)
+        self.assertEqual(1402440452.05458, float(ts))
+        self.assertEqual('2014-06-10T22:47:32.054580', ts.isoformat)
+
+        ts = utils.Timestamp.from_isoformat('1970-01-01T00:00:00.000000')
+        self.assertIsInstance(ts, utils.Timestamp)
+        self.assertEqual(0.0, float(ts))
+        self.assertEqual('1970-01-01T00:00:00.000000', ts.isoformat)
+
+        ts = utils.Timestamp(1402440452.05458)
+        self.assertIsInstance(ts, utils.Timestamp)
+        self.assertEqual(ts, utils.Timestamp.from_isoformat(ts.isoformat))
+
     def test_ceil(self):
         self.assertEqual(0.0, utils.Timestamp(0).ceil())
         self.assertEqual(1.0, utils.Timestamp(0.00001).ceil())