Once upon a time I played with comparing a stock's performance in the most recent month with some historical month.

>I remember. You looked for the "best" match, right?
Right. Then I looked to see what happened (historically) and assumed that might happen in the coming month, like this:

Click on the picture to see the tutorial

>And your predictions were pretty lousy as I recall.?
Well ... that's the problem. To see how well the prediction worked we had to wait for a month, so I thought:
"Why not pretend that 'today' is a year ago. Then we can compare our prediction with what actually happened."

>And is it any good?
The spreadsheet is here. Play with it yourself ... and decide.

Note that the example is Microsoft, where "today" is 250 days ago, about one year, and ...

>What's that Watch it happen thing, at cells K3-L3?
Uh ... if you have the time (and patience) you can watch the spreadsheet trying to match the current month with some historical month.
You get neat moving pictures like this.

>And is it any good?
Didn't I mention that you should play with it yourself? Just click on the picture of the spreadsheet to download it.