A puzzling passage from Vladimir Nabokov’s 1957 novel Pnin:

Pnin’s birthday … fell on February 3, by the Julian calendar into which he had been born in St. Petersburg in 1898. He never celebrated it nowadays, partly because, after his departure from Russia, it sidled by in a Gregorian disguise (thirteen — no, twelve days late), and partly because during the academic year he existed mainly on a motuweth frisas basis.

This describes the novelist’s own confusing situation. He’d been born in Saint Petersburg on April 10, 1899, in the Julian calendar, which corresponds to April 22, 1899, in the Gregorian. (Russia didn’t adopt the Gregorian calendar until 1918.) The turn of the century added a further wrinkle: The offset between the two calendars increased from 12 to 13 days for dates occurring after February 1900. Properly this had no effect on earlier dates, so Nabokov’s birthday should always have been reckoned April 22, but some confused writers began to give it as April 23, and eventually that’s when he began to celebrate it himself — as he told interviewers, it meant he now shared a birthday with both William Shakespeare and Shirley Temple.

(Though he nowhere explains it, “motuweth frisas” refers to the days of the week, the most familiar rhythm of an academic’s life.)