Timestamp conversion on windows fails with timestamps close to EPOCH

@pfmoore

BPO	37527
Nosy	@pfmoore, @abalkin, @tjguk, @jleclanche, @zware, @zooba, @animalize, @ammaraskar, @pganssle, @Dschoni
PRs	gh-81708: Fixing the "Invalid argument" bug on `datetime.timestamp()` #15498

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-07-09.10:32:25.056>
labels = ['3.8', 'type-bug', '3.7', '3.9', 'OS-windows']
title = 'Timestamp conversion on windows fails with timestamps close to EPOCH'
updated_at = <Date 2020-01-10.12:29:05.237>
user = 'https://github.com/Dschoni'

bugs.python.org fields:

activity = <Date 2020-01-10.12:29:05.237>
actor = 'pingchaoc'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Windows']
creation = <Date 2019-07-09.10:32:25.056>
creator = 'Dschoni'
dependencies = []
files = []
hgrepos = []
issue_num = 37527
keywords = ['patch']
message_count = 5.0
messages = ['347541', '347596', '355819', '355824', '355832']
nosy_count = 10.0
nosy_names = ['paul.moore', 'belopolsky', 'tim.golden', 'jleclanche', 'zach.ware', 'steve.dower', 'malin', 'ammar2', 'p-ganssle', 'Dschoni']
pr_nums = ['15498']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37527'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

Linked PRs

A long description of the issue can be found on SO here: https://stackoverflow.com/questions/56931738/python-crash-on-windows-with-a-datetime-close-to-the-epoch?noredirect=1#comment100413591_56931738

TL;DR:

This fails on windows:

from datetime import datetime
datetime.fromtimestamp(1).timestamp()

Looks like a similar problem to bpo-29097.

>>> from datetime import datetime
>>> d = datetime.fromtimestamp(1)
>>> d.timestamp()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 22] Invalid argument

Neijwiert tried to analyzed it in stackoverflow:
https://stackoverflow.com/questions/56931738/

This indeed seems to be a duplicate of 29097, which is fixed in Python 3.7, so we can close this bug. Thank you for your report Dschoni, and thank you for finding the duplicate Ma Lin!

bpo-29097 fixed bug in datetime.fromtimestamp().
But this issue is about datetime.timestamp(), not fixed yet.

Ah, my mistake. The examples all use datetime.fromtimestamp, so I didn't notice that it was failing only on the timestamp side. Re-opening, thanks!

Just narrowed down the problem little bit:

the error happens in the method timestamp()

only on Windows
On the native datetime object (without timezone info)
On the dates a couple of days after 1 January 1970 and all the dates before that

import datetime

dt = datetime.datetime(1970,1,3)

print(dt) # 1970-01-03 00:00:00

print(dt.timestamp()) #169200.0



dt = datetime.datetime(1970,1,1)

print(dt)  # 1970-01-01 00:00:00

print(dt.timestamp()) # OSError: [Errno 22] Invalid argument


tz =datetime.timezone.utc

dt = datetime.datetime(1970,1,1, tzinfo=tz) 

print(dt) # 1970-01-01 00:00:00+00:00

print(dt.timestamp()) # 0.0


tz =datetime.timezone.utc

dt = datetime.datetime(1960,1,1, tzinfo=tz) #1960-01-01 00:00:00+00:00

print(dt)

print(dt.timestamp()) # -315619200.0

This was tested on Windows 10 Python 3.10.5

On Ubuntu all of the tests just run

No, this needs someone who's more of an expert in time functions than me. Unless you want to wait for me to get up to speed (no promises, my learning list is pretty long).

The core problem of this issue likely also impact #94414

At least both the timestamp() and astimezone() functions are impacted on Windows 10 and Windows 11

fix(Python) Use timezone-aware timestamps in some unit tests on Windo…

I encountered this issue as well. datetime.timetuple() doesn't seem to be affected, so using it in combination with time.mktime() is a workaround:

>>> datetime.fromtimestamp(1).timestamp()
Traceback (most recent call last):
  File "<python-input-12>", line 1, in <module>
    datetime.fromtimestamp(1).timestamp()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
OSError: [Errno 22] Invalid argument
>>> time.mktime(datetime.fromtimestamp(1).timetuple())
1.0

The above drops microseconds, but taking them into account isn't that hard:

>>> dt = datetime.fromtimestamp(0.123)
>>> time.mktime(dt.timetuple())
0.0
>>> time.mktime(dt.timetuple()) + dt.microsecond / 1e6
0.123

This fails on windows:

from datetime import datetime
datetime.fromtimestamp(1).timestamp()

Issue fixed by #143463.

Python 3.15.0a5+ (heads/main:f5685a266b2, Jan 15 2026, 10:57:22) [MSC v.1944 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import datetime
>>> datetime.fromtimestamp(1).timestamp()
1.0

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Timestamp conversion on windows fails with timestamps close to EPOCH #81708

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Dschoni commented on Jul 9, 2019

animalize commented on Jul 10, 2019

pganssle commented on Nov 1, 2019

animalize commented on Nov 1, 2019

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