检查mongodb中的日期时间对象是否为UTC格式，来自python

Question

In mongodb , a field called joining_date appears as

"Sun Dec 19 2010 05:35:55 GMT+0000 (UTC)"

This as you see is a UTC date .

But the same field when accessed from pymongo appears as

 datetime.datetime(2010, 12, 19, 5, 35, 55, 286000)

From python i need to check that the date is in utc format or not.

Problem: I get a strange result as shown below

v = datetime(2010, 12, 19, 5, 35, 55, 286000)
v.tzinfo == pytz.utc # Returns False !..why ?

How can I get back the original string Sun Dec 19 2010 05:35:55 GMT+0000 (UTC) from datetime.datetime(2010, 12, 19, 5, 35, 55, 286000) or how can I check if datetime.datetime(2010, 12, 19, 5, 35, 55, 286000) is in UTC format or not ?

Answer 1

datetime objects returned by pymongo always represent a time in UTC, just as dates stored in MongoDB are always stored as (that is, assumed to be in) UTC.

pymongo can convert your datetime s automatically to be time zone aware if you set the tz_info flag to True when creating your Connection . You can then use datetime s astimezone() method to convert to another time zone if you wish.

Answer 2

To quote the PyMongo documentation:

All datetimes retrieved from the server (no matter what version of the driver you're using) will be naive and represent UTC.

ie v.tzinfo is None . You would have been warned about this if you'd tried to convert them to another timezone:

>>> v.astimezone(pytz.timezone("US/Eastern"))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: astimezone() cannot be applied to a naive datetime

However, you can get a timezone aware datetime by doing datetime(v.year, v.month, v.day, v.hour, v.minute, v.second, v.microsecond, pytz.utc) . In this case, your original code would work:

v = datetime(2010, 12, 19, 5, 35, 55, 286000, pytz.utc)
v.tzinfo == pytz.utc # Returns True