How do I translate an ISO 8601 datetime string into a Python datetime object? [duplicate]

Question

I prefer using the dateutil library for timezone handling and generally solid date parsing. If you were to get an ISO 8601 string like: 2010-05-08T23:41:54.000Z you'd have a fun time parsing that with strptime, especially if you didn't know up front whether or not the timezone was included. pyiso8601 has a couple of issues (check their tracker) that I ran into during my usage and it hasn't been updated in a few years. dateutil, by contrast, has been active and worked for me:

from dateutil import parser
yourdate = parser.parse(datestring)

Since Python 3.7 and no external libraries, you can use the strptime function from the datetime module:

datetime.datetime.strptime('2019-01-04T16:41:24+0200', "%Y-%m-%dT%H:%M:%S%z")

For more formatting options, see here.

Python 2 doesn't support the %z format specifier, so it's best to explicitly use Zulu time everywhere if possible:

datetime.datetime.strptime("2007-03-04T21:08:12Z", "%Y-%m-%dT%H:%M:%SZ")

Because ISO 8601 allows many variations of optional colons and dashes being present, basically CCYY-MM-DDThh:mm:ss[Z|(+|-)hh:mm]. If you want to use strptime, you need to strip out those variations first.

The goal is to generate a UTC datetime object.

---

If you just want a basic case that work for UTC with the Z suffix like 2016-06-29T19:36:29.3453Z:

datetime.datetime.strptime(timestamp.translate(None, ':-'), "%Y%m%dT%H%M%S.%fZ")

---

If you want to handle timezone offsets like 2016-06-29T19:36:29.3453-0400 or 2008-09-03T20:56:35.450686+05:00 use the following. These will convert all variations into something without variable delimiters like 20080903T205635.450686+0500 making it more consistent/easier to parse.

import re
# This regex removes all colons and all
# dashes EXCEPT for the dash indicating + or - utc offset for the timezone
conformed_timestamp = re.sub(r"[:]|([-](?!((\d{2}[:]\d{2})|(\d{4}))$))", '', timestamp)
datetime.datetime.strptime(conformed_timestamp, "%Y%m%dT%H%M%S.%f%z" )

---

If your system does not support the %z strptime directive (you see something like ValueError: 'z' is a bad directive in format '%Y%m%dT%H%M%S.%f%z') then you need to manually offset the time from Z (UTC). Note %z may not work on your system in Python versions < 3 as it depended on the C library support which varies across system/Python build type (i.e., Jython, Cython, etc.).

import re
import datetime

# This regex removes all colons and all
# dashes EXCEPT for the dash indicating + or - utc offset for the timezone
conformed_timestamp = re.sub(r"[:]|([-](?!((\d{2}[:]\d{2})|(\d{4}))$))", '', timestamp)

# Split on the offset to remove it. Use a capture group to keep the delimiter
split_timestamp = re.split(r"([+|-])",conformed_timestamp)
main_timestamp = split_timestamp[0]
if len(split_timestamp) == 3:
    sign = split_timestamp[1]
    offset = split_timestamp[2]
else:
    sign = None
    offset = None

# Generate the datetime object without the offset at UTC time
output_datetime = datetime.datetime.strptime(main_timestamp +"Z", "%Y%m%dT%H%M%S.%fZ" )
if offset:
    # Create timedelta based on offset
    offset_delta = datetime.timedelta(hours=int(sign+offset[:-2]), minutes=int(sign+offset[-2:]))

    # Offset datetime with timedelta
    output_datetime = output_datetime + offset_delta

Arrow looks promising for this:

>>> import arrow
>>> arrow.get('2014-11-13T14:53:18.694072+00:00').datetime
datetime.datetime(2014, 11, 13, 14, 53, 18, 694072, tzinfo=tzoffset(None, 0))

Arrow is a Python library that provides a sensible, intelligent way of creating, manipulating, formatting and converting dates and times. Arrow is simple, lightweight and heavily inspired by moment.js and requests.

You should keep an eye on the timezone information, as you might get into trouble when comparing non-tz-aware datetimes with tz-aware ones.

It's probably the best to always make them tz-aware (even if only as UTC), unless you really know why it wouldn't be of any use to do so.

#-----------------------------------------------
import datetime
import pytz
import dateutil.parser
#-----------------------------------------------

utc = pytz.utc
BERLIN = pytz.timezone('Europe/Berlin')
#-----------------------------------------------

def to_iso8601(when=None, tz=BERLIN):
  if not when:
    when = datetime.datetime.now(tz)
  if not when.tzinfo:
    when = tz.localize(when)
  _when = when.strftime("%Y-%m-%dT%H:%M:%S.%f%z")
  return _when[:-8] + _when[-5:] # Remove microseconds
#-----------------------------------------------

def from_iso8601(when=None, tz=BERLIN):
  _when = dateutil.parser.parse(when)
  if not _when.tzinfo:
    _when = tz.localize(_when)
  return _when
#-----------------------------------------------

I haven't tried it yet, but pyiso8601 promises to support this.

import datetime, time
def convert_enddate_to_seconds(self, ts):
    """Takes ISO 8601 format(string) and converts into epoch time."""
    dt = datetime.datetime.strptime(ts[:-7],'%Y-%m-%dT%H:%M:%S.%f')+\
                datetime.timedelta(hours=int(ts[-5:-3]),
                minutes=int(ts[-2:]))*int(ts[-6:-5]+'1')
    seconds = time.mktime(dt.timetuple()) + dt.microsecond/1000000.0
    return seconds

This also includes the milliseconds and time zone.

If the time is '2012-09-30T15:31:50.262-08:00', this will convert into epoch time.

>>> import datetime, time
>>> ts = '2012-09-30T15:31:50.262-08:00'
>>> dt = datetime.datetime.strptime(ts[:-7],'%Y-%m-%dT%H:%M:%S.%f')+ datetime.timedelta(hours=int(ts[-5:-3]), minutes=int(ts[-2:]))*int(ts[-6:-5]+'1')
>>> seconds = time.mktime(dt.timetuple()) + dt.microsecond/1000000.0
>>> seconds
1348990310.26