datetime.now in python different when running loca

Question

I am using Heroku to run some python code.

The code that i have written uses a predefined time like example: 16:00 and compares that with the current time and the calculates the difference like this:

now = datetime.datetime.now()
starttime = datetime.datetime.combine(datetime.date.today(), datetime.time(int(hour), int(minute)))
dif = now - starttime

Running this locally ofc uses the time in my system i guess and everything is correct. However when i post it on the server and run it there the time is one hour back. So how can i fix this so it always uses the timezone that i am in?

I live in Sweden

Thank you all, Code examples would be deeply appreciated.

EDIT1

Rest of the code looks like this:

if dif < datetime.timedelta(seconds=0):
    hmm = 3                                     
elif dif < datetime.timedelta(seconds=45*60):
    t = dif.total_seconds() / 60
    time, trash = str(t).split(".")
    time = time+"'"
elif dif < datetime.timedelta(seconds=48*60):
    time = "45'"
elif dif < datetime.timedelta(seconds=58*60):
    time = "HT"
elif dif < datetime.timedelta(seconds=103*60):
    t = (dif.total_seconds() - 840) / 60
    time, trash = str(t).split(".")
    time = time+"'"
elif dif < datetime.timedelta(seconds=108*60):
    time = "90'"
else:
    time = "FT"

and using the imports that you provided i get this error now:

AttributeError: type object 'datetime.datetime' has no attribute 'timedelta'

i tried to do like this but it did not help:

from datetime import datetime, time, timedelta

Answer 1

So how can i fix this so it always uses the timezone that i am in?

Find your timezone in the tz database e.g., using tzlocal module. Run on your local machine:

#!/usr/bin/env python
import tzlocal # $ pip install tzlocal

print(tzlocal.get_localzone().zone)

If tzlocal has been capable to get the timezone id then you should see something like: Europe/Paris. Pass this string to the server.

On the server:

#!/usr/bin/env python
from datetime import datetime, time
import pytz # $ pip install pytz

tz = pytz.timezone('Europe/Paris') # <- put your local timezone here
now = datetime.now(tz) # the current time in your local timezone
naive_starttime = datetime.combine(now, time(int(hour), int(minute)))
starttime = tz.localize(naive_starttime, is_dst=None) # make it aware
dif = now - starttime

Answer 2

That is due to server time is different from your time. For example, if you are in China and the server is in USA. datetime.now() should returns a different time for both.

datetime.datetime.now() returns a "naive datatime object", because is related to local time not a timezone.

So, you should work with a timezone throughout your application, to create a "time-zone-aware datetime object" just:

import pytz
from datetime import datetime
datetime.now(pytz.utc)

NOTE: I'm using UTC timezone, you can use whetever you want to.