Number of ways you could do this comparison.
You could create another measure for 2016 like you did for 2017 and add sale day of the week as a dimension
Or you can add a filter box with country and day of the week and just have the dimension as a year so you haven't got to hard code it.
Or perhaps a line chart with days of week as the dimension and year with a country filter to show the comparison over the course of the week.
Hope this helps