The ancients were an inquisitive lot, a characteristic shown to best effect in works like Aristotle’s Problems (‘Why do sex-maniacs’ eyelashes fall out?’) and Plutarch’s Greek and Roman Questions. Among much else, Plutarch asked, ‘Why do Romans adopt the month of January as the beginning of the new year?’

He began by doing the maths: July used to be called Quintilis, ‘Fifth’ (subsequently named after Julius Caesar) and August Sextilis, ‘Sixth’ (named after Augustus), while September to December covered the Roman numerals seven to ten.