Apple has said that it is aware of the issue and is investigating the cause so it can provide a fix. The issue seems to be affecting users who set the time on their iPhone 6s or iPhone 6s Plus manually or change time zones while traveling.
Apple is recommending users to restart their iPhone, and go to Settings > General > Date & Time and make sure that Set Automatically is turned on.
Based on this Apple discussion thread, the issue seems to be affecting a number of users. It is strange that the issue is affecting only iPhone 6s and iPhone 6s Plus.
Have you faced the problem? Let us know in the comments.