How do I set Inspiron 3647 to Auto Power On Weekdays only?

I'm able to get to area where I can set the system to power up but the options are every day or a specific day - I cannot find  the weekday option for the Inspiron 3847 or the Inspiron 3647.   All my OptiPlexes had that option.  Can you advise how I set these machines to automatically power up weekdays only?  Thanks