Issue #6491 has been updated by zombor (Jeremy Bush). And if it's not a bug, what's the difference between `%:z` and `%Z`? Currently they basically output the same thing. The documentation says: `%Z - Time zone abbreviation name`. ---------------------------------------- Bug #6491: DateTime.strftime('%Z') output is incorrect format https://bugs.ruby-lang.org/issues/6491#change-26833 Author: zombor (Jeremy Bush) Status: Rejected Priority: Low Assignee: tadf (tadayoshi funaba) Category: Target version: ruby -v: ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin11] DateTime.parse('2012/05/23').strftime('%Z') should output 'GMT' (or a similar string). It outputs "+00:00" (or a similar offset string). -- http://bugs.ruby-lang.org/