diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 9246aff12a6707..4775aa628e9385 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -915,6 +915,10 @@ 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()