Can we confirm whether this issue is not a python issue?
We are talking about small z, not capital Z.

From Python docs at http://docs.python.org/lib/module-time.html  :
"The use of %Z is now deprecated, but the %z escape that expands to the preferred hour/minute offset is not supported by all ANSI C libraries."

Most current C libraries support %z, it is in fact the preferred way to do things, would be bad to see python reject this.
Even then - isn't the above a bug? If not supported, %z should always provide a empty character, but not print out totally incorrect data as +0000 for EST.