We tend to view our basic patterns, like spending the evening out and then lying unconscious for eight hours straight, as belonging to a natural order. But until streetlights, being up late meant wandering town in butt-­clenching terror, tripping over stray animals until the wind blew out your lantern and you were set upon by armed bandits. So you went home before dark and went to bed early, waking after midnight. Much of this was forgotten until 2001, when the historian Roger Ekirch unearthed segmented sleep in the cultural history of pre-­19th-­century Europe, supporting the research of an American chronobiologist who, in a 1992 study, asserted that segmented sleep is more natural than the monophasic variety we now aspire to. Exposed over several weeks to preindustrial light conditions, most of us will gradually start sleeping twice a night, hooked to the Ur-­rhythm of our internal clock.

It was the Industrial Revolution, saturating us with electric light, that caused dorveille to obsolesce — but now it’s electricity that makes it so useful. Dorveille is the only part of the day when no one expects to hear from anyone at all. You can keep yourself unavailable without that abstract sense of guilt. You never need to open an email. Dorveille’s appeal doesn’t derive from historicity: what appeals is the escape from the very conditions that obliterated it.

At first, I treated dorveille like stolen time, and like most thieves, I was careless with my loot, frittering it away each night. But as I persisted, I saw the deeper value. Dorveille once served as a time to remember dreams. For me, the tasks undertaken in dorveille retained a little of the ease of dreaming. During the day, I can’t reliably read 20 pages in a row before I experience an overwhelming physical urge to waste my time. During dorveille, I finished books. It was like having a superpower. Nor must dorveille be all business. I found that snaggly, insoluble problems, in friendships and writing and marriage, were more easily confronted and could be muddled through for longer.

Metabolically, the alertness of dorveille differs from the taut insomniac variety. The author of that 1992 study — the one that proved the innateness of segmented sleep — described dorveille as a state of “nonanxious wakefulness,” which truly sounds oxymoronic until you experience it. I’m one of the least relaxed people I know; having lived most of my adult life in New York, “awake” and “anxious” are synonyms as far as I’m concerned. But during these hours I felt calm. Most amazing, I had no desire to reach for my phone. I felt an unfamiliar lack of itch.