[Xymon] Green status during a total blackout

Hi,

My Xymon server (running Hobbit 4.2.2) has been shut down during 6 hours. When the power came back, Xymon came back too. I've checked all monitored equipment, everything was green during the past 6h. I was expecting purple or white color because no data has been reported during the time. Is that a bug or a setting I could adjust ?

Thanks.