Version:            (using KDE 4.3.3)
Compiler:          gcc version 4.3.4 
OS:                Linux
Installed from:    Gentoo Packages

I have United Kingdom set for my region/language in system settings, but Africa/Lagos for /etc/localtime and for 'General Time and Date' KOrganizer settings in Kontact settings.

ftp://elsie.nci.nih.gov/pub/tzdata2009r.tar.gz states

# Nigeria
# Zone  NAME            GMTOFF  RULES   FORMAT  [UNTIL]
Zone    Africa/Lagos    0:13:36 -       LMT     1919 Sep
                        1:00    -       WAT

Today is 10 Nov 2009.
Starting with no std.ics file in ~/.kde4/share/apps/korganizer I start Kontact and create an event at 11:00 am on 11 Nov 2009.  This displays correctly in the month view.  Close Kontact.

The std.ics file shows:

TZID:Africa/Lagos
BEGIN:STANDARD
TZNAME:WAT
TZOFFSETFROM:+001336
TZOFFSETTO:+0100
DTSTART:19190901T234624
RDATE;VALUE=DATE-TIME:19190901T234624
END:STANDARD
END:VTIMEZONE

Main Bug: On re-starting Kontact, the event is displayed 12h 36m earlier (22:24 10 Nov).  Click to edit the event and the correct time/date is shown, and on ok/apply the event is correct in the calendar.  Upon closing Kontact, the std.ics file now shows:

TZOFFSETFROM:+1336

On changing this to 

TZOFFSETFROM:+0013

event times appear to be ok and stay ok.

Observations:  (1) I believe the TZOFFSETFROM field spec is HHMM; (2) my inexperienced reading of the tzdata above suggests that before 01 Sept 1919 Africa/Lagos was +13m36s off GMT, and after that date it was +1h off GMT; seems like it shouldn't matter if it was +13h off GMT before 1919 (as in the bug), from 1919 forward it should be +1h only -- but Korganizer looks to be adding the previous offset [certainly I bow to tz experts here, just noting it does not seem right to the naive observer].