I found yesterday the solution : I got the folder zoneinfo,replace in the path usr/share then I reboot the box. It works perfect.
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I think there isn't like an option in the hdmu image on spark7111. I don't know if it is available on other kinds.
Well,
using "HDMU_18160_OptimussOS2_OE_2987_Flash.zip" has a problem setting the timezone to GMT +2. Athens, Bucharest, etc, does not help at all. However, Jerussalem works fine :=)
Setting manually the /etc/timezone from CET to GMT or UTC does not help at all.