Now you can define a 'time-fixpoint' in the past
and the Image will generatet everytime,when
((now-fixpoint) % interval) ~ 0.
so you can say: generate it every day at 12.00.
git-svn-id: file:///home/jan/tmp/wetterstation/trunk@203 dd492736-c11a-0410-ad51-8c26713eaf7f
losinshi