I'm so glad you posted this—I have the same problem with this aphorism. I'm craving a more precise way to express this idea. Maybe "it would have been better to start five minutes ago, but starting now is better than starting in five more minutes."

19 years and 364 days ago was about 1.000137 best time (considering 20 years ago was best time 1 and now is best time 2). I know it's not preciser enough, but more pedantic answer requires more precise definition of "now" and "20 years ago".