Thank you for your reply. The return for date is the system time - which is set to UTC (as it should be)
The locale, even if it were not set, would default to system time, but in such a case a time would still be displayed albeit the wrong one.
The problem here is that no time is being displayed.
My guess is a missing or corrupt library as a result of the software update (which would not have affected any of the previously correct config settings)
My problem is not knowing where to look. As it affects both KDE and the log in manager, my wild stab would be somewhere in X