DatePropertyにはやはり不具合(bug)あり

date = db.DateTimeProperty(auto_now_add=True) の値が
対象の datastore のデータを更新する度に、時刻が進んでいってしまう現象は
以下の Patch により直った。 ( SDK 1.0.1)

DateProperty does not work properly in dev environment
http://code.google.com/p/googleappengine/issues/detail?id=131

c:/Program Files/Google/google_appengine/google/appengine/api/datastore_types.py

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I tried a patch to module datastore_types.py, which seems to work:

change line 1033
from
lambda val: datetime.datetime.fromtimestamp(float(val) / 1000000.0),
to
lambda val: datetime.datetime.utcfromtimestamp(float(val) / 1000000.0),

Per the Python doc, fromtimestamp() converts to the local timezone.

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