python
Timestamp conversion on windows fails with timestamps close to EPOCH
| BPO | 37527 |
|---|---|
| Nosy | @pfmoore, @abalkin, @tjguk, @jleclanche, @zware, @zooba, @animalize, @ammaraskar, @pganssle, @Dschoni |
| PRs |
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']
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
I think I found what the issues is. The problem seems to be in the c code function _PyTime_localtime(time_t t, struct tm *tm) in the pytime.c.
For Windows it uses localtime_s function, which appears not to accept negative time (time before 1 January 1970), however for none-windows it uses localtime_r, which does accept negative values.
To reproduce on Windows
// https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/localtime-s-localtime32-s-localtime64-s?view=msvc-170
#include <stdio.h>
#include <string.h>
#include <time.h>
int main(void)
{
struct tm newtime;
long long int long_time;
char timebuf[26];
errno_t err;
long_time = -1; // If this is 0 or above, everything just works fine
// Convert to local time.
err = localtime_s(&newtime, &long_time);
if (err)
{
printf("Invalid argument");
exit(1);
}
err = asctime_s(timebuf, 26, &newtime);
if (err)
{
printf("Invalid argument to asctime_s.");
exit(1);
}
printf("%s\n", timebuf);
}
However on Ubuntu
//https://en.cppreference.com/w/c/chrono/localtime
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
time_t t = -1000;
struct tm buf;
char str[26];
// https://manpages.ubuntu.com/manpages/bionic/man3/ctime.3.html
asctime_r(localtime_r(&t, &buf), str);
printf("Date / time: %s", str); // Date / time: Thu Jan 1 00:43:20 1970
}
@zooba , are you the right person to look at this issue, as it seems to be related to the Microsoft way of implementation of the localtime_s function ?
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 https://github.com/python/cpython/issues/94414
At least both the timestamp() and astimezone() functions are impacted on Windows 10 and Windows 11
Duplicates: https://github.com/python/cpython/issues/94414, https://github.com/python/cpython/issues/94757
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 https://github.com/python/cpython/pull/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
