Can "Trailing 5 Week Average" not kill performance?

Looking for a performance tip - I’ve built a dashboard for a metric, let’s say page views. I’d like to compare today’s page views to the same day over the past five weeks. To do this, I’m using TimeShift(). This is already pretty slow, but then I also want to average the trailing 5 weeks so I’m comparing this week’s page views to the trailing 5 week average at any given moment.

This is killing the dashboard’s performance though. Does anyone know of a simpler way to do this?