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Specify which timezone a datetime is in, in python

I have a datetime that i get from a database, this datetime is a UTC datetime. But when i pull it from the DB, it is unaware of the timezone. What i need to do, is convert this datetime to a "seconds from epoch" time for another function. The problem with this, is that the system's time is in PST and i am not able to change it for specific reasons.
So, what i want to do is, take this datetime that i get from the database, and tell python that this datetime is a UTC datetime. Every way that i have done that, results in it losing time or gaining time due to timezone conversions. Again, not trying to convert the time, just trying to specify that it is UTC.
If anyone can help with this that would be great.
Thanks!
Example
Assume database_function() returns a datetime data type that is '2013-06-01 01:06:18'
datetime = database_function()
epoch = datetime.strftime('%s')
pytz.utc.localize(database_function()).datetime.strftime('%s')
datetime.replace(tzinfo=pytz.utc).datetime.strftime('%s')
Both of these return a epoch timestamp of 1370077578
But, it SHOULD return a timestamp of 1370048778 per http://www.epochconverter.com/
Remember, this timestamp is a utc timestamp

Using the fabolous pytz:
import datetime, pytz
dt = datetime.datetime(...)
utc_dt = pytz.utc.localize(dt)
This creates a tz-aware datetime object, in UTC.

How about Setting timezone in Python This appears to reset the timezone within your python script. You are changing the time zone that your system sees given the specified time, not changing the specified time into the specified time zone. You probably want to set it to 'UTC'
time.tzset()
Resets the time conversion rules used by the library routines.
The environment variable TZ specifies how this is done.
New in version 2.3.
Availability: Unix.
I do not have this available on my home platform so I could not test it. I had to get this from the previous answer.
The answer marked best on the question is:
>>> import os, time
>>> time.strftime('%X %x %Z')
'12:45:20 08/19/09 CDT'
>>> os.environ['TZ'] = 'Europe/London'
>>> time.tzset()
>>> time.strftime('%X %x %Z')
'18:45:39 08/19/09 BST'
To get the specific values you've listed:
>>> year = time.strftime('%Y')
>>> month = time.strftime('%m')
>>> day = time.strftime('%d')
>>> hour = time.strftime('%H')
>>> minute = time.strftime('%M')
See here for a complete list of directives. Keep in mind that the strftime() function will always return a string, not an integer or other type.

You can Use pytz, which is a time zone definitions package.
from datetime import datetime
from pytz import timezone
fmt = "%Y-%m-%d %H:%M:%S %Z%z"
# Current time in UTC
now_utc = datetime.now(timezone('UTC'))
print now_utc.strftime(fmt)
# Convert to US/Pacific time zone
now_pacific = now_utc.astimezone(timezone('US/Pacific'))
print now_pacific.strftime(fmt)
# Convert to Europe/Berlin time zone
now_berlin = now_pacific.astimezone(timezone('Europe/Berlin'))
print now_berlin.strftime(fmt)
output:
2014-04-04 21:50:55 UTC+0000
2014-04-04 14:50:55 PDT-0700
2014-04-04 23:50:55 CEST+0200
or may be it helps
>> import pytz
>>> import datetime
>>>
>>> now_utc = datetime.datetime.utcnow() #Our UTC naive time from DB,
for the time being here I'm taking it as current system UTC time..
>>> now_utc
datetime.datetime(2011, 5, 9, 6, 36, 39, 883479) # UTC time in Naive
form.
>>>
>>> local_tz = pytz.timezone('Europe/Paris') #Our Local timezone, to
which we want to convert the UTC time.
>>>
>>> now_utc = pytz.utc.localize(now_utc) #Add Timezone information to
UTC time.
>>>
>>> now_utc
datetime.datetime(2011, 5, 9, 6, 36, 39, 883479, tzinfo=<UTC>) # The
full datetime tuple
>>>
>>> local_time = now_utc.astimezone(local\_tz) # Convert to local
time.
>>>
>>> local_time #Current local time in Paris
datetime.datetime(2011, 5, 9, 8, 36, 39, 883479, tzinfo=<DstTzInfo
'Europe/Paris' CEST+2:00:00 DST>)

Here is one way, using the pytz module:
import pytz
utc_datetime = (datetime.datetime(1970, 1, 1, tzinfo=pytz.utc)
+ datetime.timedelta(seconds=seconds_since_epoch)
If you don't want to install the pytz module, you can copy the example UTC class from the datetime documentation (search for "class UTC"):
https://docs.python.org/2/library/datetime.html#tzinfo-objects

Here's stdlib only solution without 3-party modules.
.., this datetime is a UTC datetime. But when i pull it from the DB, it is unaware of the timezone. What i need to do, is convert this datetime to a "seconds from epoch" time for another function.emphasize is mine
To convert an unaware (naive) datetime object that represents time in UTC to POSIX timestamp:
from datetime import datetime
timestamp = (dt_from_db - datetime(1970, 1, 1)).total_seconds()
Example:
>>> from datetime import datetime
>>> dt = datetime.strptime('2013-06-01 01:06:18', '%Y-%m-%d %H:%M:%S')
>>> (dt - datetime(1970, 1, 1)).total_seconds()
1370048778.0
See Converting datetime.date to UTC timestamp in Python that provides solutions for various Python versions.
To answer the question from the title: In general you need pytz library to handle timezones in Python. In particular, you should use .localize method to convert an unaware datetime object into timezone-aware one.
import pytz # $ pip install pytz
from tzlocal import get_localzone # $ pip install tzlocal
tz = get_localzone() # local timezone whatever it is (just an example)
aware_dt = tz.localize(naive_dt_in_local_timezone, is_dst=None)
is_dst=None asserts that naive_dt_in_local_timezone exists and unambiguous.
Though you don't need it for UTC timezone because it always has the same UTC offset (zero) around the year and in all past years:
import pytz
aware_dt = utc_dt.replace(tzinfo=pytz.utc)
See Python - simplest and most coherent way to get timezone-aware current time in UTC? (it provides a stdlib-only solution):
aware_dt = utc_dt.replace(tzinfo=timezone.utc)

Get timezone used by datetime.datetime.fromtimestamp()

Is it possible, and if yes, how, to get the time zone (i.e. the UTC offset or a datetime.timezone instance with that offset) that is used by datetime.datetime.fromtimestamp() to convert a POSIX timestamp (seconds since the epoch) to a datetime object?
datetime.datetime.fromtimestamp() converts a POSIX timestamp to a naive datetime object (i.e. without a tzinfo), but does so using the system's locale to adjust it to the local timezone and the UTC offset that was in effect at that time.
For example, using the date 2008-12-27 midnight UTC (40 * 356 * 86400 seconds since the epoch):
>>> datetime.datetime.fromtimestamp(40 * 356 * 86400)
datetime.datetime(2008, 12, 27, 1, 0)
That timestamp is converted to a datetime object at 1 o'clock in the morning (which it was at that time, here in an CET/CEST timezone). 100 days later, this is the result:
>>> datetime.datetime.fromtimestamp((40 * 356 + 100) * 86400)
datetime.datetime(2009, 4, 6, 2, 0)
Which is 2 o'clock in the morning. This is because by then, DST was active.
I'd expected that datetime.datetime.fromtimestamp() would set the tzinfo it uses in the returned datetime instance, but it doesn't.

datetime.fromtimestamp(ts) converts "seconds since the epoch" to a naive datetime object that represents local time. tzinfo is always None in this case.
Local timezone may have had a different UTC offset in the past. On some systems that provide access to a historical timezone database, fromtimestamp() may take it into account.
To get the UTC offset used by fromtimestamp():
utc_offset = fromtimestamp(ts) - utcfromtimestamp(ts)
See also, Getting computer's utc offset in Python.

From the Python documentation:
classmethod datetime.fromtimestamp(timestamp, tz=None)
Return the local date and time corresponding to the POSIX timestamp, such as is returned by time.time(). If optional argument tz is None or not specified, the timestamp is converted to the platform’s local date and time, and the returned datetime object is naive.
Else tz must be an instance of a class tzinfo subclass, and the timestamp is converted to tz‘s time zone. In this case the result is equivalent to tz.fromutc(datetime.utcfromtimestamp(timestamp).replace(tzinfo=tz)).
The key part of this description as it relates to your question is that when you don't specify a time zone, not only does it use the local time zone, but the result is naive. You seem to want it to be aware.
This is a particular distinction made by Python, and is discussed right at the very top of the datetime documentation.
If what you want is a datetime that is aware of the local time zone, try the tzlocal library. It is focused on that particular problem. See also this question.

If you know the timezone of the timestamp you want to convert, you can simply send it in while calling fromtimestamp:
>>> from datetime import datetime
>>> import pytz
>>>
>>> datetime.fromtimestamp(1562684265, pytz.timezone("Europe/Stockholm"))
datetime.datetime(2019, 7, 9, 16, 57, 45, tzinfo=<DstTzInfo 'Europe/Stockholm' CEST+2:00:00 DST>)
>>>
>>> datetime.fromtimestamp(1562684265, pytz.timezone("UTC"))
datetime.datetime(2019, 7, 9, 14, 57, 45, tzinfo=<UTC>)

Using time.gmtime you can extract the timezone as described in this previous answer: Get TZ information of the system in Python?.
>>> from __future__ import print_function
>>> from time import gmtime, strftime
>>> print(strftime("%z", gmtime()))
-0600
Prints -06:00 for my CST laptop in both python-2.7 and python-3.3
You can also use localtime() to get a local time struct.
>>> from __future__ import print_function
>>> from time import localtime
>>> lt = localtime()
>>> print(lt.tm_zone)
"CDT"
>>> print(lt.tm_gmtoff/(60*60))
-5.0
>>> print(lt.tm_gmtoff/(60*60) - (1 if lt.tm_isdst == 1 else 0)) # Adjusted for DST
-6.0
Hope this helps

Localizing Epoch Time with pytz in Python

Im working on converting epoch timestamps to dates in different timezones with pytz. What I am trying to do is create a DateTime object that accepts an Olson database timezone and an epoch time and returns a localized datetime object. Eventually I need to answer questions like "What hour was it in New York at epoch time 1350663248?"
Something is not working correctly here:
import datetime, pytz, time
class DateTime:
def __init__(self, timezone, epoch):
self.timezone = timezone
self.epoch = epoch
timezoneobject = pytz.timezone(timezone)
datetimeobject = datetime.datetime.fromtimestamp( self.epoch )
self.datetime = timezoneobject.localize(datetimeobject)
def hour(self):
return self.datetime.hour
if __name__=='__main__':
epoch = time.time()
dt = DateTime('America/Los_Angeles',epoch)
print dt.datetime.hour
dt = DateTime('America/New_York',epoch)
print dt.datetime.hour
This prints the same hour, whereas one should be 3 or so hours ahead. Whats going wrong here? I'm a total Python beginner, any help is appreciated!

datetime.fromtimestamp(self.epoch) returns localtime that shouldn't be used with an arbitrary timezone.localize(); you need utcfromtimestamp() to get datetime in UTC and then convert it to a desired timezone:
from datetime import datetime
import pytz
# get time in UTC
utc_dt = datetime.utcfromtimestamp(posix_timestamp).replace(tzinfo=pytz.utc)
# convert it to tz
tz = pytz.timezone('America/New_York')
dt = utc_dt.astimezone(tz)
# print it
print(dt.strftime('%Y-%m-%d %H:%M:%S %Z%z'))
Or a simpler alternative is to construct from the timestamp directly:
from datetime import datetime
import pytz
# get time in tz
tz = pytz.timezone('America/New_York')
dt = datetime.fromtimestamp(posix_timestamp, tz)
# print it
print(dt.strftime('%Y-%m-%d %H:%M:%S %Z%z'))
It converts from UTC implicitly in this case.

For creating the datetime object belonging to particular timezone from a unix timestamp, you may pass the pytz object as a tz parameter while creating your datetime. For example:
>>> from datetime import datetime
>>> import pytz
>>> datetime.fromtimestamp(1350663248, tz= pytz.timezone('America/New_York'))
datetime.datetime(2012, 10, 19, 12, 14, 8, tzinfo=<DstTzInfo 'America/New_York' EDT-1 day, 20:00:00 DST>)
You can get the list of all timezones using pytz.all_timezones which returns exhaustive list of the timezone names that can be used.
Also take a look at List of tz database time zones wiki.

epochdt = datetime.datetime.fromtimestamp(epoch)
timezone1 = timezone("Timezone/String")
adjusted_datetime = timezone1.localize(epochdt)
Working from memory, so excuse any syntax errors, but that should get you on the right track.
EDIT: Missed the part about knowing the hour,etc. Python has great Time/Date Formatting. At pretty much the bottom of that link is the table showing how to pull different attributes from the datetime object.

Python date iso8601 format with timezone designator

I'm sending some dates from server that has it's time in gmt-6 format, but when i convert them to isoformat i don't get the tz designator at the end.
I'm currently setting the date like this:
date.isoformat()
but I'm getting this string: 2012-09-27T11:25:04 without the tz designator.
how can I do this?

You're not getting the timezone designator because the datetime is not aware (ie, it doesn't have a tzinfo):
>>> import pytz
>>> from datetime import datetime
>>> datetime.now().isoformat()
'2012-09-27T14:24:13.595373'
>>> tz = pytz.timezone("America/Toronto")
>>> aware_dt = tz.localize(datetime.now())
>>> datetime.datetime(2012, 9, 27, 14, 25, 8, 881440, tzinfo=<DstTzInfo 'America/Toronto' EDT-1 day, 20:00:00 DST>)
>>> aware_dt.isoformat()
'2012-09-27T14:25:08.881440-04:00'
In the past, when I've had to deal with an unaware datetime which I know to represent a time in a particular timezone, I've simply appended the timezone:
>>> datetime.now().isoformat() + "-04:00"
'2012-09-27T14:25:08.881440-04:00'
Or combine the approaches with:
>>> datetime.now().isoformat() + datetime.now(pytz.timezone("America/Toronto")).isoformat()[26:]
'2012-09-27T14:25:08.881440-04:00'

It is much easier to deal with dates with a specialized module such as arrow or delorean
>>> import arrow
>>> arrow.now().isoformat()
'2020-11-25T08:10:39.672624+01:00'

From a timezone and a UTC time, get the difference in seconds vs local time at that point in time

This should be very simple, but I can't quite figure it out in Python.
I want to have a function which takes two arguments, a UTC time in seconds and a zoneinfo name like 'Europe/Vienna' and returns the offset in seconds from local time and UTC for that point in time.
In C it would be:
/* ... code to to set local time to the time zone I want to compare against,
not shown here. Then call function below to get difference vs localtime.
Hardly an ideal solution,
but just to demonstrate what I want in a "lingua franca" (C): */
int get_diff_vs_localtime(const time_t original_utc_time)
{
struct tm* ts;
ts = localtime(&original_utc_time);
return mktime(ts) - original_utc_time;
}
I guess my question really boils down to: "given an Olson timezone (example 'Europe/Stockholm') and a UTC time, what is the local time?

Assuming "UTC time in seconds" means POSIX timestamp. To convert it to Stockholm time:
from datetime import datetime
import pytz
tz = pytz.timezone('Europe/Stockholm')
utc_dt = datetime.utcfromtimestamp(posix_timestamp).replace(tzinfo=pytz.utc)
dt = tz.normalize(utc_dt.astimezone(tz))
print(dt.strftime('%Y-%m-%d %H:%M:%S %Z%z'))
tz.normalize() is unnecessary if the source timezone is UTC (like in this case).
A simpler alternative is to use fromtimestamp()'s tz parameter, to convert "seconds since the epoch" to local time:
from datetime import datetime
import pytz
tz = pytz.timezone('Europe/Stockholm')
dt = datetime.fromtimestamp(posix_timestamp, tz)
print(dt.strftime('%Y-%m-%d %H:%M:%S %Z%z'))
Both examples produce the same result.
If local machine uses "right" timezones then to convert POSIX timestamp received from an external source to UTC, an explicit formula could be used:
from datetime import datetime, timedelta
import pytz
utc_dt = datetime(1970, 1, 1, tzinfo=pytz.utc) + timedelta(seconds=posix_timestamp)
The latest formula may also support a larger date range (less likely issues with dates before 1970, after 2038 or 3000 years).
If the timestamp comes from the local "right" source then the first two examples should be used instead (they call "right" time.gmtime()).

You could use pytz and datetime to do something in the manner of:
from datetime import datetime
from pytz import timezone
def get_diff(now, tzname):
tz = timezone(tzname)
utc = timezone('UTC')
utc.localize(datetime.now())
delta = utc.localize(now) - tz.localize(now)
return delta
Which for the following example...
now = datetime.utcnow()
print(now)
tzname = 'Europe/Stockholm'
delta = get_diff(now, tzname)
print(delta)
now_in_stockholm = now + delta
print(now_in_stockholm)
... outputs:
2012-10-02 14:38:56.547475
2:00:00
2012-10-02 16:38:56.547475

This is pretty old, but I couldn't find a great answer, so here's what I came up with:
from datetime import datetime
local = datetime.now()
utc = datetime.utcnow()
int((local - utc).days * 86400 + round((local - utc).seconds, -1))
Returns:
-21600
because I am (currently) 21600 seconds (6 hours) behind UTC.
Note: the second date calculated (in this case UTC) needs to be rounded since there is a super small difference in time at each calculation.

I guess my question really boils down to: "given an Olson timezone
(example 'Europe/Stockholm') and a UTC time, what is the local time?
If I understand your problem correctly:
from pytz import timezone
import datetime, time
tz = timezone('Asia/Kuwait')
utc_dt = datetime.datetime.utcfromtimestamp(time.time())
utc_dt + tz.utcoffset(utc_dt)
>>> tz.utcoffset(utc_dt).seconds
10800
>>> tz
<DstTzInfo 'Asia/Kuwait' LMT+3:12:00 STD>
>>> utc_dt + tz.utcoffset(utc_dt)
datetime.datetime(2012, 10, 2, 17, 13, 53, 504322)
>>> utc_dt
datetime.datetime(2012, 10, 2, 14, 13, 53, 504322)