[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

Change by STINNER Victor :


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stage: patch review -> resolved
status: open -> closed

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

STINNER Victor  added the comment:


New changeset a847785b40ed8819bde2dac5849dc31d15e99a74 by Victor Stinner in 
branch 'main':
  bpo-43869: Time Epoch is the same on all platforms (GH-30664)
https://github.com/python/cpython/commit/a847785b40ed8819bde2dac5849dc31d15e99a74


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[issue43869] Fix documentation of epoch/time.time

[Irit Katriel]

Change by Irit Katriel :


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versions: +Python 3.11 -Python 3.10, Python 3.6, Python 3.7, Python 3.8, Python 
3.9

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

STINNER Victor  added the comment:

I was going to close the change, but I had a last look and... oh... I found 
that the Python test suite checks that the Epoch is 1970-01-01 at 00:00 since 
2008! I wrote GH-30664 to add an explicit test and I updated the doc.

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

Change by STINNER Victor :


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pull_requests: +28865
pull_request: https://github.com/python/cpython/pull/30664

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

STINNER Victor  added the comment:


New changeset ff7703c4b609a697ada8165fd1c52a73404b6d07 by Miguel Brito in 
branch 'main':
bpo-43869: Improve epoch docs (GH-25777)
https://github.com/python/cpython/commit/ff7703c4b609a697ada8165fd1c52a73404b6d07


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[issue43869] Fix documentation of epoch/time.time

[Miguel Brito]

Miguel Brito  added the comment:

Seen that no one is working on this issue I created an PR to clarify the docs.

https://github.com/python/cpython/pull/25777

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[issue43869] Fix documentation of epoch/time.time

[Miguel Brito]

Change by Miguel Brito :


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keywords: +patch
nosy: +miguendes
nosy_count: 4.0 -> 5.0
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stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/25777

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

STINNER Victor  added the comment:

"platform dependent" was added in 2017 by the commit (bpo-29026): 

commit 23557d59b819f57800ddef0b1373acef8e024670
Author: Eric Appelt 
Date:   Thu Feb 16 05:00:45 2017 -0500

bpo-29026: Clarify documentation of time.time (#34)

* bpo-29026: Clarity documentation of time.time

Clarify the documentation of time.time by more
precisely defining what is meant by "seconds since
the epoch" on most platforms. Additionally explain
how gmtime and localtime may be used to extract
calendar components and convert to a more common
date format.

* bpo-29026: Minor improvements for time.time doc

* bpo-29026: Consistency fixes for time.time doc

---

MS-DOS (no longer supported by Python since 2014) uses 1980-01-01 epoch.

The Windows FILETIME type uses 1601-01-01 epoch. Python has convention 
functions to the Unix 1970-01-01 Epoch:

static __int64 secs_between_epochs = 11644473600; /* Seconds between 1.1.1601 
and 1.1.1970 */

static void
FILE_TIME_to_time_t_nsec(FILETIME *in_ptr, time_t *time_out, int* nsec_out)
{
/* XXX endianness. Shouldn't matter, as all Windows implementations are 
little-endian */
/* Cannot simply cast and dereference in_ptr,
   since it might not be aligned properly */
__int64 in;
memcpy(, in_ptr, sizeof(in));
*nsec_out = (int)(in % 1000) * 100; /* FILETIME is in units of 100 
nsec. */
*time_out = Py_SAFE_DOWNCAST((in / 1000) - secs_between_epochs, 
__int64, time_t);
}

void
_Py_time_t_to_FILE_TIME(time_t time_in, int nsec_in, FILETIME *out_ptr)
{
/* XXX endianness */
__int64 out;
out = time_in + secs_between_epochs;
out = out * 1000 + nsec_in / 100;
memcpy(out_ptr, , sizeof(out));
}

More epochs for more fun:
https://en.wikipedia.org/wiki/Epoch_(computing)#Notable_epoch_dates_in_computing

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

STINNER Victor  added the comment:

time.time doc says "On Windows and most Unix systems, the epoch is January 1, 
1970, 00:00:00 (UTC)"

The epoch doc says "For Unix, the epoch is January 1, 1970, 00:00:00 (UTC)".

At least, the epoch doc can be completed to also mention that it's the same on 
Windows.

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[issue43869] Fix documentation of epoch/time.time

[STINNER Victor]

STINNER Victor  added the comment:

On Windows 10 (build 20H2), I get:

Python 3.10.0a7+ (heads/master:b136b1aac4, Apr 16 2021, 14:36:39) [MSC v.1928 
64 bit (AMD64)] on win32
>>> import time
>>> time.gmtime(0)
time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=0, tm_min=0, 
tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)

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[issue43869] Fix documentation of epoch/time.time

[Ofek Lev]

New submission from Ofek Lev :

The descriptions for the following:

- https://docs.python.org/3/library/time.html#epoch
- https://docs.python.org/3/library/time.html#time.time

indicate that it is platform dependent. However, that is likely untrue. See the 
brief discussion here: 
https://github.com/DataDog/integrations-core/pull/6692#discussion_r427469097

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assignee: docs@python
components: Documentation
messages: 391214
nosy: Ofekmeister, docs@python, p-ganssle
priority: normal
severity: normal
status: open
title: Fix documentation of epoch/time.time
type: enhancement
versions: Python 3.10, Python 3.6, Python 3.7, Python 3.8, Python 3.9

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