`'UTC{0:+}'.format(offset)`

I’m afraid it’s kinda bad (→`UTC+1.0`), and error prone.  Personally, I would generate ISO 8601-compatible dates — ignore locales and everything, and just generate:

    2014-03-24T14:44:10+01:00

to describe ~now in CET.  For UTC, do:

    2014-03-24T13:44:10+00:00
    --- or ---
    2014-03-24T13:44:10Z

(that `T` might be replaced with a space.)