What does "no time like the present, there's" mean?

Do or say it now, as in Go ahead and call him—there's no time like the present. This adage was first recorded in 1562. One compiler of proverbs, John Trusler, amplified it: “No time like the present, a thousand unforeseen circumstances may interrupt you at a future time” (Proverbs Exemplified, 1790).