1926 is the date Amelia Bones gives for what she suspects to be Quirrell's true identity. It is also the date of Tom Marvolo Riddle's birth in canon. This and other details suggest that Bones believes Quirrell is Riddle. But for that to be true, it must be that during Voldemort's first campaign, Riddle was still appearing as Riddle until, apparently, 1973

Bones must not know Riddle is Voldemort, or she would be behaving very differently towards Dumbledore. Dumbledore, on the other hand, appears to believe Riddle is Voldemort, because just a few chapters ago he told the Marauder's Map to find Tom Riddle when he was looking for Voldemort. Therefore Dumbledore must not know Quirrell is Riddle. It's maddening how many problems could be solved here by the characters' sharing information with each other.

Anyway, given that Riddle is Bones' hero, much of what Riddle told Hermione may have been perfectly truthful. And here is what especially caught my eye:

I stopped trying to be a hero, and went off to do something else I found more pleasant.

So it sounds like Riddle initially created Voldemort so he could make himself into a hero, but then decided to be Voldemort full-time, because it would be more fun. This he did for eight years, from 1973-1981.

Similarly, Riddle previously told Harry (in chapters nineteen and twenty) that he decided not to become a Dark Lord, and that he realized that if he did everything necessary to do that Dark Lord gig right, there would be no point. What if he was telling the truth? What if Riddle decided to dispose of the Voldemort persona because it stopped being fun?

Personally, the thought of someone totally amoral and willing to totally change around their plans based on what is most fun is rather frightening.

EDIT: See also this comment of mine, which lays out the story I am proposing in chronological order. Note that my confidence in what Riddle was originally planning on doing when he first went full-time as Voldemort, and my confidence in his motives for abandoning the Voldemort persona, is lower than my confidence in the rest of my theory.