>>> from pymongo import MongoClient
>>> client = MongoClient('mongodb://****:*****@localhost:27017/')
>>> db = client.test_database
>>> import datetime
>>> print datetime.datetime.utcnow()

2016-10-21 14:42:16.964096

>>> test = {"date": datetime.datetime.utcnow()}
>>> print test

{'date': datetime.datetime(2016, 10, 21, 14, 42, 23, 39207)}

>>> db.tests.insert_one(test)

<pymongo.results.InsertOneResult object at 0x7f4f7f9ee780>

>>> print test

{'date': datetime.datetime(2016, 10, 21, 14, 42, 23, 39207), '_id': ObjectId('580a2963f79060731570bdd4')}

>>> print db.tests.find_one({"_id": test['_id']})

{u'date': datetime.datetime(2016, 10, 21, 14, 42, 23, 39000), u'_id': ObjectId('580a2963f79060731570bdd4')}