Known sourcecanonical
"Junius, Aprilis, Septémq; Nouemq; tricenos, Vnum plus reliqui, Februs tenet octo vicenos, At si bissextus fuerit superadditur vnus."
William Harrison / Description of Britain (prefixed to Holinshed's "Chronicle," 1577).
Description of Britain (prefixed to Holinshed's "Chronicle," 1577).
Bartlett's Familiar Quotations, 9th ed. (Little, Brown, 1905), public domain