When is next Monday

On my home computer (Xubuntu 14.04), I have

zev@home:~$ date +%F
2015-10-05

zev@home:~$ date +%F -d "next Monday"
2015-10-12

whereas at work (Red Hat 5.11), I have

zev@work:~$ date +%F
2015-10-05

zev@work:~$ date +%F -d "next Monday"
2015-10-05

(Note that today is Monday.) My initial guess was that the different interpretations of the phrase next Monday are due to the systems having different versions of the coreutil date:

zev@home:~$ date --version | head -2
date (GNU coreutils) 8.21
Copyright (C) 2013 Free Software Foundation, Inc.

zev@work:~$ date --version | head -2
date (GNU coreutils) 5.97
Copyright (C) 2006 Free Software Foundation, Inc.

My questions are:

• Is the difference in versions of the date program the sole cause, or is there something else about a system that will affect its interpretation of date strings?

• How can I know whether a system will have one interpretation or the other, without running the commands to check directly? If the only thing that affects the outcome is the version of date, then according to this unix.SE thread (Which version of X introduced feature Y?) I should be able to find which version introduced the new behavior in a changelog for the date program, but I can't find anything remotely like that here (maybe I'm just confused).