Thanks for the heads-up. Rather than add that tzset call, which is a bit of a 
hack, I'd rather make parse_datetime2 more reentrant so that it's immune to this 
problem. So I installed this:

http://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=4e6e16b3f43ce96302b1e52e48730c1f15e18c14

into Gnulib to improve the parse_datetime2 API, and installed the attached 
patches into coreutils. This uncovered a bug in one of our recently-added test 
cases, which the attached patches also fix.