fix(storage): fix incorrect mtime by UTC offset

google/cloud/storage/_helpers.py

@@ -19,6 +19,7 @@
 
 import base64
 from hashlib import md5
+from datetime import datetime
 import os
 
 from google.cloud.storage.constants import _DEFAULT_TIMEOUT
@@ -297,3 +298,17 @@ def _base64_md5hash(buffer_object):
     _write_buffer_to_hash(buffer_object, hash_obj)
     digest_bytes = hash_obj.digest()
     return base64.b64encode(digest_bytes)
+
+
+def _convert_to_timestamp(value):
+    """Convert non-none datetime to timestamp.
+
+    :type value: :class:`datetime.datetime`
+    :param value: The datetime to convert.
+
+    :rtype: int
+    :returns: The timestamp.
+    """
+    utc_naive = value.replace(tzinfo=None) - value.utcoffset()
+    mtime = (utc_naive - datetime(1970, 1, 1)).total_seconds()
+    return mtime

google/cloud/storage/blob.py

@@ -31,8 +31,8 @@
 from io import BytesIO
 import mimetypes
 import os
-import time
 import warnings
+import six
 
 from six.moves.urllib.parse import parse_qsl
 from six.moves.urllib.parse import quote
@@ -57,6 +57,7 @@
 from google.cloud.storage._helpers import _get_storage_host
 from google.cloud.storage._helpers import _PropertyMixin
 from google.cloud.storage._helpers import _scalar_property
+from google.cloud.storage._helpers import _convert_to_timestamp
 from google.cloud.storage._signing import generate_signed_url_v2
 from google.cloud.storage._signing import generate_signed_url_v4
 from google.cloud.storage.acl import ACL
@@ -846,7 +847,10 @@ def download_to_filename(
 
         updated = self.updated
         if updated is not None:
-            mtime = time.mktime(updated.timetuple())
+            if six.PY2:
+                mtime = _convert_to_timestamp(updated)
+            else:
+                mtime = updated.timestamp()
             os.utime(file_obj.name, (mtime, mtime))
 
     def download_as_string(self, client=None, start=None, end=None, raw_download=False):

tests/unit/test_blob.py

@@ -1060,7 +1060,7 @@ def test_download_to_file_w_chunks_w_raw(self):
 
     def _download_to_filename_helper(self, updated, raw_download):
         import os
-        import time
+        from google.cloud.storage._helpers import _convert_to_timestamp
         from google.cloud._testing import _NamedTemporaryFile
 
         blob_name = "blob-name"
@@ -1080,7 +1080,10 @@ def _download_to_filename_helper(self, updated, raw_download):
                 self.assertIsNone(blob.updated)
             else:
                 mtime = os.path.getmtime(temp.name)
-                updated_time = time.mktime(blob.updated.timetuple())
+                if six.PY2:
+                    updated_time = _convert_to_timestamp(blob.updated)
+                else:
+                    updated_time = blob.updated.timestamp()
                 self.assertEqual(mtime, updated_time)
 
         headers = {"accept-encoding": "gzip"}