Parse "Z" timezone suffix in datetime

NumesSanguis · February 25, 2020, 2:48pm

Most have been said here already, just wanted to add that I also arrived at this page after receiving JSON data from a JavaScript application.

Also, using dateutil gives a slightly different result. Compare:

import dateutil.parser as dt
date_time_obj = dt.parse('2020-02-25T13:13:43.913Z')
date_time_obj
# out: datetime.datetime(2020, 2, 25, 13, 13, 43, 913000, tzinfo=tzutc())

date_time_obj2 = datetime.fromisoformat('2020-02-25T13:13:43.913Z'.replace('Z', '+00:00'))
date_time_obj2
# out: datetime.datetime(2020, 2, 25, 13, 13, 43, 913000, tzinfo=datetime.timezone.utc)

A difference in tzinfo with tzutc() vs datetime.timezone.utc.
Although that doesn’t seem to be a problem:

date_time_obj == date_time_obj2
# out: True

borpin · June 4, 2020, 8:37am

It would be really useful if the documentation explicitly stated that Z is not parsed and must be replaced with +00:00

seb · October 27, 2020, 3:02am

I think one thing that might be worth to add is that Django’s DjangoJSONEncoder also uses ‘Z’. This is the reason that I ended up here.

So it’s not just other popular languages like Javascript that uses the format. One of the most popular Python web frameworks uses it for JSON encoding datetimes.

ndamclean · January 13, 2021, 8:51pm

I wanted to note that the replace('Z', '00+00') workaround makes parsing dates around 5x as slow (I ran a benchmark of various date parsing libraries and functions; see linked gist).

I think having a very fast ISO parsing function in the python standard library is important.

Date parsing benchmark (requires packages: pytest, pytest-benchmark, python-dateutil, ciso8601, iso8601)

gist.github.com

https://gist.github.com/ndamclean/2c1113ea40199be7edd43a506748ffd7

bench_dateparse.py

import ciso8601
import iso8601
import pytest
from datetime import datetime
from dateutil import parser


TIME_STR = '2019-08-28T14:34:25.518993+00:00'
TIME_STR_Z = '2019-08-28T14:34:25.518993Z'

This file has been truncated. show original

dimaqq · July 21, 2021, 12:48am

Another gotcha is that datetime.datetime.fromisoformat is picky about fractional seconds:

2020-01-01T12:33:56
2020-01-01T12:33:56.0
2020-01-01T12:33:56.000 (milliseconds)
2020-01-01T12:33:56.0000
2020-01-01T12:33:56.000000 (microseconds)
2020-01-01T12:33:56.00000 # commonly generated by JavaScript libraries
2020-01-01T12:33:56.0000000
2020-01-01T12:33:56.000000000 (nanoseconds) # golang, tc39 Temporal