One of the earliest occurrences of the word "atom" to mean the smallest possible unit of measuring time is found in the Greek text of the New Testament in Paul's 1 Corinthians 15:52. The text compares the length of time of the “atom” to the time needed for "the twinkling of an eye." The text reads: "en atomo, en repe ophthamou" – the word "atom" is usually translated "a moment" — "In a moment, in the twinkling of an eye". With that meaning, it was later referred to in Medieval philosophical writings as the smallest possible division of time. The earliest known occurrence in English is in Byrhtferth's Enchiridion (a science text) of 1010–1012,^[2] where it was defined as 1/564 of a momentum (1½ minutes),^[3] and thus equal to almost 160 milliseconds. It was used in the computus, the calculation used to determine the calendar date of Easter.^{[citation needed]}

• Planck time