>>> db.issue.filter(None, { "due_date": "2008-02-29"})['1', '2', '3', '4', '5', '6', '7', 

etc.

>>> db.issue.get("1", "due_date")
<Date 2008-01-10.00:00:00.000>
>>> db.issue.get("2", "due_date")
>>> db.issue.get("3", "due_date")
<Date 2007-11-30.00:00:00.000>

Clearly something is wrong here. Other dates work just fine:

>>> db.issue.filter(None, { "due_date": "2008-02-28"})
['149']
>>> db.issue.get("149", "due_date")
<Date 2008-02-28.00:00:00.000>
>>> db.issue.filter(None, { "due_date": "2008-03-01"})
['222']
>>> db.issue.get("222", "due_date")
<Date 2008-03-01.00:00:00.000>