import datetime, time

from ndb import model, tasklets

EPOCH = datetime.datetime.utcfromtimestamp(0)
OFFSET = datetime.timedelta(seconds=7 * 60 * 60)  # Offset between PDT and UTC

def to_utc(value):
  return value + OFFSET

def from_utc(value):
  return value - OFFSET

class UtcDateTimeProperty(model.DateTimeProperty):

  def _db_set_value(self, v, p, value):
    value = to_utc(value)
    super(UtcDateTimeProperty, self)._db_set_value(v, p, value)

  def _db_get_value(self, v, p):
    value = super(UtcDateTimeProperty, self)._db_get_value(v, p)
    value = from_utc(value)
    return value

class Record(model.Model):
  utc = UtcDateTimeProperty()

def main():
  # Disable caching.
  ctx = tasklets.get_context()
  ctx.set_cache_policy(False)
  ctx.set_memcache_policy(False)

  now = datetime.datetime.now()
  print 'now =', now
  r = Record(utc=now)
  print 'r =', r
  r.put()
  print 'r.key =', r.key
  print r._to_pb()
  print 'posix time * 1000000 =', hex(int(time.time() * 1000000))

  q = r.key.get()
  assert q is not r  # Actually read from datastore
  print 'q =', q
  print 'q.utc =', q.utc
  assert q.utc == now

if __name__ == '__main__':
  main()