This is just an easy way to visualize what the market's performance is (in price or percent) in any given session for any chosen time frame. The magnitude of price moves are not the same today as they were 50 years ago, which is why I included the percent selection to better compare historical movements. Time frame selections are Daily, Weekly, Monthly, Quarterly, and Yearly. I added in a little background highlight to show the start of a new session as well.
The source code is open so feel free to poke around!