I have a S7-1200 with KTP 400 comfort and use the plc as the clock master (synchronize the HMI with the the S7-1200 through area pointer). However, whenever I leave the system turned off for 2~3 days, it loses the time adjustment, and starts in 1970 or something like this... do you know what is going on? Can this be a hardware problem (the capacitor that supplies power to the clock), or is there some additional setting I need to make?

Thanks in advance,