Why datetime.now() is not returning correct value

[mfarees...@gmail.com]

Hi.

I am in Asia/Karachi timezone and am testing my application for US/Pacific timezone. Here is the scenario:

The system time that I've set is,

    2016-03-24 18:02:58

    and the timezone is US/Pacific

When I use the Python interpreter to print the datetime, I get 

>>> print datetime.datetime.now()

2016-03-24 18:02:58.814000

>>> print datetime.datetime.utcnow()

2016-03-25 01:02:58.814000

Which is correct. But when I use my web2py application to print the same I get,

print datetime.datetime.now()       # 2016-03-25 06:02:58.814000

print datetime.datetime.utcnow()  # 2016-03-25 01:02:58.814000

So, the problem is that the two datetime.now() results do not match. For some reason, the application is returning a datetime which is 12 hours ahead of what it should actually return. I'm facing this issue on a Windows machine; but on Linux Mint, I'm getting correct results.

This seems like its a tricky one, who's up for a challenge? : )

[Niphlod]

how do you run the web2py application ? utc times match perfectly, it's just the timezone that is not matching... environmental variables ?!

[mfarees...@gmail.com]

I start the web2py server using this command

    python web2py.py

The I go to localhost:8000/app_name

I haven't set any timezone value in the environment variable, so I guess it should be default. However, I have set the system time and timezone from the bottom right clock.

[Leonel Câmara]

When I use the Python interpreter to print the datetime, I get 

>>> print datetime.datetime.now()

2016-03-24 18:02:58.814000

>>> print datetime.datetime.utcnow()

2016-03-25 01:02:58.814000

How is this correct if your timezone is not UTC?

[mfarees...@gmail.com]

Pacific Time (US & Canada (UTC -08:00) is the selected timezone. When it's 6:00 PM in LA, its 1:00 AM (of the next day) UTC. There's a 7 hour difference between LA and UTC (since DayLight Saving is active right now). Hence, the results quoted are correct.

[Leonel Câmara]

But that shows a 9 hour difference.

[mfarees...@gmail.com]

No, it doesn't. 6:00 PM + 7 hrs = 1:00 AM (of next day).

[Leonel Câmara]

Nevermind I clearly needed more coffee.

This is weird. Why would calling it in web2py be different. I can't replicate this. Is it possible web2py was launched before you changed the timezone?.

[mfarees...@gmail.com]

Yes, that's exactly what happened. I did not restart web2py after changing the timezone and I don't want to do that too. I want the correct time dynamically, without having to restart the server.

[mfarees...@gmail.com]

Here is some more info on this. The datetime module does not return the correct time if the timezone is changed, unless the Python instance is restarted.
 http://bugs.python.org/issue17627

[Leonel Câmara]

Humm if you don't mind installing python for windows extensions. You could try:

import platform

import datetime

if platform.system() == 'Windows':

    from win32timezone import TimeZoneInfo, TimeZoneDefinition

    localnow = datetime.datetime.now(TimeZoneInfo(TimeZoneDefinition.current()[1]))

else:

    localnow = datetime.datetime.now()

print localnow