Update docstring - pruned or replaced dead links and described fallback behavior (not yet fully implemented)
Update docstring - pruned or replaced dead links and described fallback behavior (not yet fully implemented)

pganssle/dateutil-test-codecov,mjschultz/dateutil,sprymix/dateutil,jenshnielsen/dateutil,Bachmann1234/dateutil,abalkin/dateutil,pganssle/dateutil-test-codecov,abalkin/dateutil,sprymix/python-dateutil