Very often I need (for logging purposes, legal
international action confirmation display, ...) quickly
a stable/constant/technical/international timezone info
in addition to %c / .asctime.  And find me regularly
checking if the computer/server displays %Z nice,
writing 10-liner funcs ...

found %z by trial (and in footnote)

yet time.strftime('%c %z') flickers (on Windows..)

think, %z can be computed very easily independent of OS
libs? time.altzone /% 3600 ... ==> "+/-HHMM" ?

that could be doc'ed.

( the sign of  time.timezone / time.altzone is
unfortunately revers of RFC standardds , yet its ok
doced. there should be a function/update-function for
long running apps also ? )

then .asctime_tz() would be very nice to find it in the
docs.  (and maybe asctime_TZ)

-robert

Could you provide a test case and clearer description of your feature
request?

(I'm somewhat away from all that currently - and not aware if newest
Python versions already solved but:)

* a "time.asctime_tz([tim])" or so should deliver a full OS-indep.
_world_ time string incl. numeric timezone info like 
"Sat Mar 21 10:33:36 2009 +0000"
It should accept a 10-tuple (like urlopen_file.info().getdate_tz('date'),
or a time.time() float time, 
or interpret a 9-tuple as GMTIME/UTC.

* strftime("%z") should be supported on all OS - _constant numeric_
format "+0000" 

* strftime("%C",[tim]) should be like asctime_tz.
  it should accept as 2nd parameter a 10-tuple alternatively, 
  or a time.time() universal float time, 
  or interpret the 9-tuple as LOCALTIME as it were.

test cases to add: 
* simple render a variation of constant tuples/float_times to constant
result strings.

Would issue9527 address your request?  Note that datetime.strftime already supports %z:

>>> from datetime import *
>>> datetime.now(timezone.utc).strftime('%c %z')
'Mon Sep 13 13:43:19 2010 +0000'

(I assume you meant to write %c, not %C.)