Thirty-some years ago ago, I plugged the time for my most recent 10K into a formula that applied regression analysis to give me a likely marathon time. Which was handy, because it spared me the effort of actually racing a marathon.

I have just discovered that there are now all sorts of calculators on the web that do a different but similar thing: they take your current, old-guy time and—theoretically, at least—convert it to its equivalent when you were young and quick.

So I plugged in what I thought I might be able to manage over a mile by April or May (9:00) pushed the button, and learned that the equivalent is (was?) 6:40. Which would really have stunk when I was a yoot. How about 7:00, which was somewhere in the area the last time I ran a slightly backed-off actual timed mile back when I was a sprightly 60? The equivalent is 5:10. Which also would have stunk. So how fast does this thing say I have to run to manage something remotely respectable? Six minutes! This means four laps of 90 seconds each. Can I ever do this? Ha-ha. I’ll be thrilled if I can get to that 9-minute mile.

Which, of course, I’ll tell people was a 6:40.