Bug report

Bug description:

Subsequent datetime.now() may return the same moment in time.

from datetime import datetime, UTC

now1 = datetime.now(UTC)
for i in range(10_000):
    a = i
now2 = datetime.now(UTC)

assert now1 < now2

    assert now1 < now2
           ^^^^^^^^^^^
AssertionError

This does seem to work as expected:

from time import sleep
from datetime import datetime, UTC

now1 = datetime.now(UTC)
sleep(0.000_000_001)
now2 = datetime.now(UTC)

assert now1 < now2

I'm not sure if this is a bug, but at least it's a documentation issue.
There's nothing in the docs explicitly indicating this behavior.

CPython versions tested on:

3.12

Operating systems tested on:

Windows

Linked PRs

• gh-124832: Add a note to indicate that datetime.now may return the same instant #124834
• [3.13] gh-124832: Add a note to indicate that datetime.now may return the same instant (GH-124834) #125145
• [3.12] gh-124832: Add a note to indicate that datetime.now may return the same instant (GH-124834) #125146