I have solved it by using a calculated dimension for time. I have a button bar with the different possible time dimensions (day, month, quarter and year) I have assigned a parameter to the button bar.
In my graph objects i use this calculated dimension as category.
On the objects I have created a dynamic filter that uses the parameter to decide which time period to show.
In my data i have a flag for last day of month, last day of quarter and last day of year. I use these in the dynamic filter
//Fredrik