By clicking on this button, Saturday and Sunday will appear in the entry sheet.
This button is available in the 
When the plan is displayed by day or month, this button allows you to view it view week.
It is possible that the display granularity has been set by default via the checkbox. 
Default granularity of the 
Global configuration
This button allows you to return to a view when scheduling remaining work scheduling remaining work displayed by month or day. The last granularity displayed will always be the one displayed on the next visit.
It is not possible to display weeks over a period of more than 52 weeks (1 year).
With the view , it is possible to quickly display the current month or the next 12 months by hovering over this line.
It is possible that the display granularity has been set by default via the checkbox. Default granularity of the Global configuration