[O] Tasks don't repeat correctly if system-time-locale is set to certain languages

[Bruce V. Chiarelli]

Hello all,

I've noticed some unusual behavior with repeating entries when the
system-time-locale variable is set. Specifically:

It is Sunday, today, October 30th. I did not mark this task, which is
a habit, yesterday.

-- If I have (setq system-time-locale "hu_HU.utf8"), Hungarian, then
marking this task DONE

* TODO Anki basic reviews                                       :habit:study:
  SCHEDULED: <2016-10-29 szo .+1d>

v----becomes----v

* TODO Anki basic reviews                                       :habit:study:
  SCHEDULED: <2016-10-30 v .+1d>

Which is not correct. I marked it DONE today, so it should repeat tomorrow.

-- If I have (setq system-time-locale "es_MX.utf8"), Mexican Spanish,
then doing the same thing:

* TODO Anki basic reviews                                       :habit:study:
  SCHEDULED: <2016-10-29 szo .+1d>

v----becomes----v

* TODO Anki basic reviews                                       :habit:study:
  SCHEDULED: <2016-10-31 lun .+1d>

Which *is* correct. I have tried this with an unset
system-time-locale, and with it set to fa_IR, es_MX, en_GB, and hu_HU.
So far, hu_HU is the only one that behaves incorrectly. Note that it
doesn't seem to matter which language the day-of-the-week abbreviation
is already in, since every time I tried this, I reverted the file back
to the Hungarian line. Changing the date to <2016-10-29 Sat .+1d>
before marking it also had no effect.

Of course, I could just set the date locale to "C" or unset it, but
there's still a bug somewhere.

I am running the 1399f5 revision now, but I can reproduce this
behavior all the way back until version 7,

Cheers,
Bruce V C