That's a tough one because you want to plot two different time periods at the same point on the axis. What I would do is a SQL Expression which subtracts one year from the current date. That way you'll actually get the data for the second year appearing as if it was in the first year. You're also going to have to create another SQL Expression that just extracts the actual year from the date. Then you'll need to plot two lines with each line being from only one of the years. It's pretty tricky stuff, but that is the approach I would take.