#17571: remove broken links in datetime.py docstring.

Lib/datetime.py

-"""Concrete date/time and related types -- prototype implemented in Python.
+"""Concrete date/time and related types.
 
-See http://www.zope.org/Members/fdrake/DateTimeWiki/FrontPage
-
-See also http://dir.yahoo.com/Reference/calendars/
-
-For a primer on DST, including many current DST rules, see
-http://webexhibits.org/daylightsaving/
-
-For more about DST than you ever wanted to know, see
-ftp://elsie.nci.nih.gov/pub/
-
-Sources for time zone and DST data: http://www.twinsun.com/tz/tz-link.htm
-
-This was originally copied from the sandbox of the CPython CVS repository.
-Thanks to Tim Peters for suggesting using it.
+See http://www.iana.org/time-zones/repository/tz-link.html for
+time zone and DST data sources.
 """
 
 import time as _time