On Wed, Aug 26, 2015 at 12:30 PM, Guido van Rossum <guido@python.org> wrote:

Why is this needed? When would a real app use %Z%z?

Given that a bug report [1] exists, someone was tripped by the current behavior. It is my understanding that "UTC" is one of the few timezone abbreviations that we recognize in strptime and the users expect strptime to be able to parse whatever strftime produces. [1]: http://bugs.python.org/issue22241