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