I'm facing a python timezones problem and am unsure of what is the right approach to deal with it. I have to calculate timedeltas from given start and end DateTime objects. It can happen that daylight saving time will change during the runtime of my events, so I have to take that into account.
So far I've learned that for this to work I need to save my start and end times as timezone aware DateTime objects rather than regular UTC DateTimes.
I've been looking into DateTime.tzinfo, pytz,and dateutil but from what I understand these are all mostly focused on localised display of UTC DateTime objects or calculating the offsets between different timezones. Other helpers I found expect the timezone as a UTC offset, so would already require me to know if a date is affected by daylight saving or not.
So, I guess my question is: Is there a way so save a DateTime as "Central Europe" and have it be aware of daytime savings when doing calculations with them? Or, if not, what would be the established way to check if two DateTime objects are within daylight saving, so I can manually adjust the result if necessary?
I'd be grateful for any pointers.
You just need to produce an aware (localised) datetime instance, then any calculation you do with it will take DST into account. Here as an example with pytz:
>>> import pytz
>>> from datetime import *
>>> berlin = pytz.timezone('Europe/Berlin')
>>> d1 = berlin.localize(datetime(2023, 3, 25, 12))
datetime.datetime(2023, 3, 25, 12, 0, tzinfo=<DstTzInfo 'Europe/Berlin' CET+1:00:00 STD>)
>>> d2 = berlin.localize(datetime(2023, 3, 26, 12))
datetime.datetime(2023, 3, 26, 12, 0, tzinfo=<DstTzInfo 'Europe/Berlin' CEST+2:00:00 DST>)
>>> d2 - d1
datetime.timedelta(seconds=82800)
>>> (d2 - d1).total_seconds() / 60 / 60
23.0
Is it possible to apply timezone when parsing ms to datetime?
My parsing is working but it is displaying local time instead of datetime with timezone:
timestamp = datetime.fromtimestamp(float(dt) / 1000.0,
tz=pytz.timezone("America/Sao_Paulo"))
Not sure if it is happening because timezone from my OS.
This just parses the timestamp as the tz you provide (so it assumes dt is a local time). If dt is absolute / UTC and you want to convert it to a local timezone, you need to first parse it it to a UTC datetime then move its timezone:
datetime.fromtimestamp(timestamp, pytz.utc).astimezone(pytz.timezone('America/Sao_Paulo'))
For instance using 1234567890:
>>> datetime.fromtimestamp(ts, pytz.utc)
datetime.datetime(2009, 2, 13, 23, 31, 30, tzinfo=<UTC>)
>>> datetime.fromtimestamp(ts, pytz.utc).astimezone(pytz.timezone('America/Sao_Paulo'))
datetime.datetime(2009, 2, 13, 21, 31, 30, tzinfo=<DstTzInfo 'America/Sao_Paulo' -02-1 day, 22:00:00 DST>)
Also note that for various historical reasons properly using pytz is not as simple as that (e.g.). If you're going to have to deal with timezones a lot, you may want to take a look at pendulum which tries to make timezone manipulations more reliable, and to provide a friendlier API.
Not sure what the problem is, it seems to be working as expected. My local time is 09:02 and with the Sao Paolo timezone it shows as 10:02, which seems correct.
>>> import datetime, time, pytz
>>> tz_1 = pytz.timezone("America/Sao_Paulo")
>>> tz_1
<DstTzInfo 'America/Sao_Paulo' LMT-1 day, 20:54:00 STD>
>>> now = time.time()
>>> now
1554382930.1575696
>>> datetime.datetime.fromtimestamp(now)
datetime.datetime(2019, 4, 4, 9, 2, 10, 157570)
>>> datetime.datetime.fromtimestamp(now, tz=tz_1)
datetime.datetime(2019, 4, 4, 10, 2, 10, 157570, tzinfo=<DstTzInfo 'America/Sao_Paulo' -03-1 day, 21:00:00 STD>)
Could you elaborate on which part is not displaying as you expected?
I want to convert a datetime with US/Eastern timezone to Budapest/Europe timezone this way:
import pytz
from datetime import datetime
ET = pytz.timezone('US/Eastern')
CET = pytz.timezone('Europe/Budapest')
time = datetime(2013, 04, 18, 0, 0, tzinfo=ET)
newTime = time.astimezone(CET)
This results newTime being: datetime.datetime(2013, 4, 18, 7, 0, tzinfo=<DstTzInfo 'Europe/Budapest' CEST+2:00:00 DST>), but it should be 2013,04,18,6,0 according to time.is and timeanddate.com converters. What do I do wrong ?
This is because of the Daylight Saving Time issue. The time passed to datetime is in the ET, not EDT, hence the result.
Take a look at pytz documentation, the preferred way is to use localize method, rather than passing tzinfo. You'll get the expected result if you amend your code to use the following line:
time = ET.localize(datetime(2013, 04, 18, 0, 0))
US/Eastern is an alias. Perhaps pytz treats it as fixed to EST instead of EDT? I'm not sure. But try America/New_York and see if that is better.
I want to compare UTC timestamps from a log file with local timestamps. When creating the local datetime object, I use something like:
>>> local_time=datetime.datetime(2010, 4, 27, 12, 0, 0, 0,
tzinfo=pytz.timezone('Israel'))
I want to find an automatic tool that would replace thetzinfo=pytz.timezone('Israel') with the current local time zone.
Any ideas?
In Python 3.x, local timezone can be figured out like this:
>>> import datetime
>>> print(datetime.datetime.now(datetime.timezone.utc).astimezone().tzinfo)
AEST
It's a tricky use of datetime's code .
For python < 3.6, you'll need
>>> import datetime
>>> print(datetime.datetime.now(datetime.timezone(datetime.timedelta(0))).astimezone().tzinfo)
AEST
Try dateutil, which has a tzlocal type that does what you need.
to compare UTC timestamps from a log file with local timestamps.
It is hard to find out Olson TZ name for a local timezone in a portable manner. Fortunately, you don't need it to perform the comparison.
tzlocal module returns a pytz timezone corresponding to the local timezone:
from datetime import datetime
import pytz # $ pip install pytz
from tzlocal import get_localzone # $ pip install tzlocal
tz = get_localzone()
local_dt = tz.localize(datetime(2010, 4, 27, 12, 0, 0, 0), is_dst=None)
utc_dt = local_dt.astimezone(pytz.utc) #NOTE: utc.normalize() is unnecessary here
Unlike other solutions presented so far the above code avoids the following issues:
local time can be ambiguous i.e., a precise comparison might be impossible for some local times
utc offset can be different for the same local timezone name for dates in the past. Some libraries that support timezone-aware datetime objects (e.g., dateutil) fail to take that into account
Note: to get timezone-aware datetime object from a naive datetime object, you should use*:
local_dt = tz.localize(datetime(2010, 4, 27, 12, 0, 0, 0), is_dst=None)
instead of:
#XXX fails for some timezones
local_dt = datetime(2010, 4, 27, 12, 0, 0, 0, tzinfo=tz)
*is_dst=None forces an exception if given local time is ambiguous or non-existent.
If you are certain that all local timestamps use the same (current) utc offset for the local timezone then you could perform the comparison using only stdlib:
# convert a naive datetime object that represents time in local timezone to epoch time
timestamp1 = (datetime(2010, 4, 27, 12, 0, 0, 0) - datetime.fromtimestamp(0)).total_seconds()
# convert a naive datetime object that represents time in UTC to epoch time
timestamp2 = (datetime(2010, 4, 27, 9, 0) - datetime.utcfromtimestamp(0)).total_seconds()
timestamp1 and timestamp2 can be compared directly.
Note:
timestamp1 formula works only if the UTC offset at epoch (datetime.fromtimestamp(0)) is the same as now
fromtimestamp() creates a naive datetime object in the current local timezone
utcfromtimestamp() creates a naive datetime object in UTC.
I was asking the same to myself, and I found the answer in 1:
Take a look at section 8.1.7: the format "%z" (lowercase, the Z uppercase returns also the time zone, but not in the 4-digit format, but in the form of timezone abbreviations, like in [3]) of strftime returns the form "+/- 4DIGIT" that is standard in email headers (see section 3.3 of RFC 2822, see [2], which obsoletes the other ways of specifying the timezone for email headers).
So, if you want your timezone in this format, use:
time.strftime("%z")
[1] http://docs.python.org/2/library/datetime.html
[2] https://www.rfc-editor.org/rfc/rfc2822#section-3.3
[3] Timezone abbreviations: http://en.wikipedia.org/wiki/List_of_time_zone_abbreviations , only for reference.
The following appears to work for 3.7+, using standard libs:
from datetime import timedelta
from datetime import timezone
import time
def currenttz():
if time.daylight:
return timezone(timedelta(seconds=-time.altzone),time.tzname[1])
else:
return timezone(timedelta(seconds=-time.timezone),time.tzname[0])
First get pytz and tzlocal modules
pip install pytz tzlocal
then
from tzlocal import get_localzone
local = get_localzone()
then you can do things like
from datetime import datetime
print(datetime.now(local))
Here's a way to get the local timezone using only the standard library, (only works in a *nix environment):
>>> '/'.join(os.path.realpath('/etc/localtime').split('/')[-2:])
'Australia/Sydney'
You can use this to create a pytz timezone:
>>> import pytz
>>> my_tz_name = '/'.join(os.path.realpath('/etc/localtime').split('/')[-2:])
>>> my_tz = pytz.timezone(my_tz_name)
>>> my_tz
<DstTzInfo 'Australia/Sydney' LMT+10:05:00 STD>
...which you can then apply to a datetime:
>>> import datetime
>>> now = datetime.datetime.now()
>>> now
datetime.datetime(2014, 9, 3, 9, 23, 24, 139059)
>>> now.replace(tzinfo=my_tz)
>>> now
datetime.datetime(2014, 9, 3, 9, 23, 24, 139059, tzinfo=<DstTzInfo 'Australia/Sydney' LMT+10:05:00 STD>)
Here's a slightly more concise version of #vbem's solution:
from datetime import datetime as dt
dt.utcnow().astimezone().tzinfo
The only substantive difference is that I replaced datetime.datetime.now(datetime.timezone.utc) with datetime.datetime.utcnow(). For brevity, I also aliased datetime.datetime as dt.
For my purposes, I want the UTC offset in seconds. Here's what that looks like:
dt.utcnow().astimezone().utcoffset().total_seconds()
Avoiding non-standard module (seems to be a missing method of datetime module):
from datetime import datetime
utcOffset_min = int(round((datetime.now() - datetime.utcnow()).total_seconds())) / 60 # round for taking time twice
utcOffset_h = utcOffset_min / 60
assert(utcOffset_min == utcOffset_h * 60) # we do not handle 1/2 h timezone offsets
print 'Local time offset is %i h to UTC.' % (utcOffset_h)
To create an ISO formatted string that includes the ISO representation of your local time zone in Israel (+04:00) :
on a server in Israel:
>>> datetime.now(datetime.now().astimezone().tzinfo).isoformat()
'2021-09-07T01:02.030042+04:00'
This will create a "timezone aware" date object that will compare to any other datetime object in UTC or local time appropriately. But the time zone ISO representation (and the date/time string itself) will change if you ran this on a server in San Francisco at the exact same time, as I did:
on a server in San Francisco, CA, USA (Pacific):
>>> datetime.now(datetime.now().astimezone().tzinfo).isoformat()
'2021-09-06T14:01:02.030042-07:00'
The datetime objects in in both cases would be compatible with each other. So if you subtracted them you'd get a time delta of 0:
On a server anywhere in Python3.6+:
>>> (datetime.fromisoformat('2021-09-06T14:01:02.030042-07:00') -
... datetime.fromisoformat('2021-09-07T01:01:02.030042+04:00'))
datetime.timedelta(0)
Based on Thoku's answer above, here's an answer that resolves the time zone to the nearest half hour (which is relevant for some timezones eg South Australia's) :
from datetime import datetime
round((round((datetime.now()-datetime.utcnow()).total_seconds())/1800)/2)
Based on J. F. Sebastian's answer, you can do this with the standard library:
import time, datetime
local_timezone = datetime.timezone(datetime.timedelta(seconds=-time.timezone))
Tested in 3.4, should work on 3.4+
You may be happy with pendulum
>>> pendulum.datetime(2015, 2, 5, tz='local').timezone.name
'Israel'
Pendulum has a well designed API for manipulating dates. Everything is TZ-aware.
I have also been looking for a simple way to read the local host configuration and get timezone aware local_time based on it. As of python 3.6+ the simplest approach is use dateutil.tz which will read /etc/localtime and assist in getting timezone aware datetime object.
Here is more info on it: https://dateutil.readthedocs.io/en/stable/tz.html
The implementation to accomplish what you're looking for is as follows:
from datetime import datetime
from dateutil import tz
local_time = datetime.now(tz.gettz())
This will provide you the following local_time:
2019-10-18 13:41:06.624536-05:00
Additional Resources I used in researching this topic:
Paul Ganssle Presentation about time zones:
https://www.youtube.com/watch?v=l4UCKCo9FWY
pytz: The Fastest Footgun in the West
https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html
I want to compare UTC timestamps from a log file with local timestamps
If this is your intent, then I wouldn't worry about specifying specific tzinfo parameters or any additional external libraries. Since Python 3.5, the built in datetime module is all you need to create a UTC and a local timestamp automatically.
import datetime
f = "%a %b %d %H:%M:%S %Z %Y" # Full format with timezone
# tzinfo=None
cdatetime = datetime.datetime(2010, 4, 27, 12, 0, 0, 0) # 1. Your example from log
cdatetime = datetime.datetime.now() # 2. Basic date creation (default: local time)
print(cdatetime.strftime(f)) # no timezone printed
# Tue Apr 27 12:00:00 2010
utctimestamp = cdatetime.astimezone(tz=datetime.timezone.utc) # 1. convert to UTC
utctimestamp = datetime.datetime.now(tz=datetime.timezone.utc) # 2. create in UTC
print(utctimestamp.strftime(f))
# Tue Apr 27 17:00:00 UTC 2010
localtimestamp = cdatetime.astimezone() # 1. convert to local [default]
localtimestamp = datetime.datetime.now().astimezone() # 2. create with local timezone
print(localtimestamp.strftime(f))
# Tue Apr 27 12:00:00 CDT 2010
The '%Z' parameter of datetime.strftime() prints the timezone acronym into the timestamp for humans to read.
For simple things, the following tzinfo implementation can be used, which queries the OS for time zone offsets:
import datetime
import time
class LocalTZ(datetime.tzinfo):
_unixEpochOrdinal = datetime.datetime.utcfromtimestamp(0).toordinal()
def dst(self, dt):
return datetime.timedelta(0)
def utcoffset(self, dt):
t = (dt.toordinal() - self._unixEpochOrdinal)*86400 + dt.hour*3600 + dt.minute*60 + dt.second + time.timezone
utc = datetime.datetime(*time.gmtime(t)[:6])
local = datetime.datetime(*time.localtime(t)[:6])
return local - utc
print datetime.datetime.now(LocalTZ())
print datetime.datetime(2010, 4, 27, 12, 0, 0, tzinfo=LocalTZ())
# If you're in the EU, the following datetimes are right on the DST change.
print datetime.datetime(2013, 3, 31, 0, 59, 59, tzinfo=LocalTZ())
print datetime.datetime(2013, 3, 31, 1, 0, 0, tzinfo=LocalTZ())
print datetime.datetime(2013, 3, 31, 1, 59, 59, tzinfo=LocalTZ())
# The following datetime is invalid, as the clock moves directly from
# 01:59:59 standard time to 03:00:00 daylight savings time.
print datetime.datetime(2013, 3, 31, 2, 0, 0, tzinfo=LocalTZ())
print datetime.datetime(2013, 10, 27, 0, 59, 59, tzinfo=LocalTZ())
print datetime.datetime(2013, 10, 27, 1, 0, 0, tzinfo=LocalTZ())
print datetime.datetime(2013, 10, 27, 1, 59, 59, tzinfo=LocalTZ())
# The following datetime is ambigous, as 02:00 can be either DST or standard
# time. (It is interpreted as standard time.)
print datetime.datetime(2013, 10, 27, 2, 0, 0, tzinfo=LocalTZ())
tzlocal from dateutil.
Code example follows. Last string suitable for use in filenames.
>>> from datetime import datetime
>>> from dateutil.tz import tzlocal
>>> str(datetime.now(tzlocal()))
'2015-04-01 11:19:47.980883-07:00'
>>> str(datetime.now(tzlocal())).replace(' ','-').replace(':','').replace('.','-')
'2015-04-01-111947-981879-0700'
>>>
First, note that the question presents an incorrect initialization of an aware datetime object:
>>> local_time=datetime.datetime(2010, 4, 27, 12, 0, 0, 0,
... tzinfo=pytz.timezone('Israel'))
creates an invalid instance. One can see the problem by computing the UTC offset of the resulting object:
>>> print(local_time.utcoffset())
2:21:00
(Note the result which is an odd fraction of an hour.)
To initialize an aware datetime properly using pytz one should use the localize() method as follows:
>>> local_time=pytz.timezone('Israel').localize(datetime.datetime(2010, 4, 27, 12))
>>> print(local_time.utcoffset())
3:00:00
Now, if you require a local pytz timezone as the new tzinfo, you should use the tzlocal package as others have explained, but if all you need is an instance with a correct local time zone offset and abbreviation then tarting with Python 3.3, you can call the astimezone() method with no arguments to convert an aware datetime instance to your local timezone:
>>> local_time.astimezone().strftime('%Y-%m-%d %H:%M %Z %z')
'2010-04-27 05:00 EDT -0400'
now_dt = datetime.datetime.now()
utc_now = datetime.datetime.utcnow()
now_ts, utc_ts = map(time.mktime, map(datetime.datetime.timetuple, (now_dt, utc_now)))
offset = int((now_ts - utc_ts) / 3600)
hope this will help you.