Noun
the name of the day that is added during a leap year
Source: WordNetAll later writers, including Macrobius about 430, Bede in 725, and other medieval computists (calculators of Easter), continued to state that the bissextum (bissextile day) occurred before the last five days of February. Source: Internet
Mart. was the day after the bissextile day. Source: Internet
The Alexandrian calendar adapted the Egyptian calendar by adding a 6th epagomenal day as the last day of the year in every fourth year, falling on 29 August preceding a Julian bissextile day. Source: Internet
There is debate about the exact position of the bissextile day in the early Julian calendar. Source: Internet
There is no doubt that the bissextile day eventually became the earlier of the two days for most purposes. Source: Internet
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. Source: Internet