[tz] [time zone problem about 2017c]

[Zefram]

Zhouyuxiang wrote:
>Now I'm wondering if this is mistake. And what are the influences?

It was a mistake.  Prior to 2017c, Africa/Juba was a link to
Africa/Khartoum, because South Sudan (Juba) and Sudan (Khartoum)
had identical timezone history.  (They were one country until 2011.)
But recently Sudan announced that it's changing from UT+3h to UT+2h,
effective 2017-11-01, and South Sudan is not changing to match,
so these two can no longer be linked.  2017c is the first with the
new Africa/Khartoum information, and so Africa/Juba had to become a
distinct zone.  With it ceasing to be a link, its entry in "backzone"
should have been removed, but that was mistakenly not done.  No one
noticed in advance of release because few people use "backzone".

-zefram