The table below assumes a Julian leap day of 29 February, but the Julian leap day ( the bissextile day ) was " ante diem bis sextum Kalendas Martias " in Latin or 24 February ( see Julian reform ), so dates between 24 and 29 February in all leap years were irregular.
12.
The leap day of the Byzantine calendar was obtained in an identical manner to the bissextile day of the original Roman version of the Julian calendar, by doubling the sixth day before the calends of March, i . e ., by doubling 24 February ( numbering the days of a month from its beginning and hence the leap day of 29 February was an invention of the late Middle Ages ).
13.
This may indicate that a single nundinal letter was assigned to both halves of the 48-hour bissextile day by this time, so that the Regifugium and the market day might fall on the same date but on different days . In any case, the 8-day nundinal cycle began to be displaced by the 7-day week in the first century AD, and dominical letters began to appear alongside nundinal letters in the fasti.
