Skip dates in Matrix visual

[ik3000]

Hi!

I have visulization that shows some data by hour and date (see below) 

I need create same kind of visual but it should show dates in 7 days increments, in other words: skip 6 dates.
Something like this (example report from another system):

How can this be done?
Thank you in advance

[lbendlin]

Add a WEEKDAY() calculated column, add it as a visual filter, set it to 5.