Minor update to doc

Author: haukex

Doc/library/time.rst

@@ -391,7 +391,9 @@ Functions
 .. function:: sleep_until(secs)
 
    Like :func:`sleep`, but sleep until the specified time of the system clock (as
-   returned by :func:`time`).
+   returned by :func:`time`). This can be used, for example, to schedule events
+   at a specific timestamp obtained from
+   :meth:`datetime.timestamp <datetime.datetime.timestamp>`.
 
    See the notes in :func:`sleep` on the behavior when interrupted and on accuracy.
    Additional potential sources of inaccuracies include: