Definition of "kalends"

My book with Professor [John Ronald Reuel] Tolkien – any book in collaboration with that great but dilatory and unmethodical man – is dated, I fear, to appear on the Greek Kalends!

1950 January 12, C[live] S[taples] Lewis, “Letters: 1950 [To Sister Penelope CSMV (BOD)]”, in Walter Hooper, editor, The Collected Letters of C. S. Lewis, volumes III (Narnia, Cambridge and Joy 1950–1963), New York, N.Y.: HarperSanFrancisco, HarperCollins, pages 5–6

The interesting thing about these ceremonies is that they must have originated in a period when the Romans were using true lunar months based on the observation of the crescent moon. The Kalends then would have been the day after the evening on which the crescent had been first sighted, the Nones would have been the first day when the moon was at the first quarter [...] In the calendar of the late Republic the lunar months have disappeared and the days have been fixed into a rigid pattern.

1967, Agnes Kirsopp Michels, “The Pre-Julian Calendar”, in The Calendar of the Roman Republic, Princeton, N.J.: Princeton University Press, part I (The Calendar of the First Century B.C.), page 21

[March, May, Quintilis, and October] also have their Nones on the seventh, as Numa [Pompilius] ordained, because Julius [Caesar] changed nothing about them. As for January, Sextilis, and December, they still have their Nones on the fifth, though they began to have thirty-one days after Caesar added two days to each, and it is nineteen days from their Ides to the following Kalends, because in adding the two days Caesar did not want to insert them before either the Nones or the Ides, lest an unprecedented postponement mar religious observance associated with the Nones or Ides themselves, which have a fixed date.

2011, Macrobius, chapter 14, in Robert A. Kaster, transl., Saturnalia (Loeb Classical Library), Cambridge, Mass., London: Harvard University Press, book I, section 9, page 171