The self, a friend once informed me, is an illusion. We were 19 at the time, and he was reading Foucault, but that was 18 years ago, and now he doesn’t think he understood Foucault back then. “It’s real,” my friend says of the self, “but it’s made.”

Whether or not the self is real or an illusion, made or found, we do know that the self we encounter in a book, even if that book is a diary, is a made thing. And not every keeper of a diary is capable of creating a self on the page. Many diaries are, in fact, ­remarkably devoid of any evidence of self. I’m thinking, for instance, of the diary of a frontier woman I found in an Iowa archive. Some climate scientists had shown interest in this diary, the archivist told me, because its descriptions of the weather were so thorough. I didn’t read that ­diary, as I ­already knew, from all my encounters with amateur writing (including my own childhood diary), what it’s like to go looking for a self and find only weather.

Heidi Julavits once said that keeping a diary when she was young is what made her a writer. Julavits, the author of four novels, ­revisits that story in the opening pages of her latest work, “The Folded Clock.” She tells of returning to her childhood diaries ­after making that claim, looking for ­evidence of the writer she would ­become. “The actual diaries, however, fail to corroborate the myth I’d concocted for ­myself,” she admits. “They reveal me to possess the mind, not of a future writer, but of a future paranoid tax auditor. I exhibited no imagination, no trace of a style, no wit, no personality.” With “The ­Folded Clock,” she corrects the ­record. Keeping a ­diary may not have made her a writer, but becoming a writer has made it ­possible for her to produce, now, an exquisite diary.

This diary is a diary in the way that Thomas De Quincey’s “Confessions of an English Opium Eater” is a confession, or that Daniel Defoe’s “A Journal of the Plague Year” is a journal, or that Sei Shonagon’s “Pillow Book” is a pillow book. Meaning it is, and it isn’t. “The Folded Clock” refuses one of the primary conventions of the diary: chronology. The entry for July 16 is followed by Oct. 18, which is followed by June 18. Time moves loosely forward, so that the final entries occur a year or two after the initial entries, but time loops and circles forward.