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

gh-124832: Add a note to indicate that `datetime.now` may return the same instant (GH-124834)

* Update datetime.rst

* Update datetime.rst

replace warning with note

* Update Doc/library/datetime.rst



* Update Doc/library/datetime.rst



---------

(cherry picked from commit 760b1e1)

Co-authored-by: spacemanspiff2007 <[email protected]>
Co-authored-by: Victor Stinner <[email protected]>
Co-authored-by: Bénédikt Tran <[email protected]>

Author: 4 people

Doc/library/datetime.rst

@@ -896,6 +896,10 @@ Other constructors, all class methods:
 
    This function is preferred over :meth:`today` and :meth:`utcnow`.
 
+   .. note::
+
+      Subsequent calls to :meth:`!datetime.now` may return the same
+      instant depending on the precision of the underlying clock.
 
 .. classmethod:: datetime.utcnow()