Comment 1 for bug 142784

The regexp '(^\|[^%])%z' makes no sense, and (^|[^%])%z' seems to work better.

I would be interested in knowing why the much simpler "format.replace('%Z', '%0+05d' % (diff/36))" isn't used. That at least doesn't take 20 minutes to debug by carefully analyzing regexps and seems to do what is needed, which is to replace %Z with the timezone... ;)