1. bissextile - Noun
2. bissextile - Adjective
Leap year; every fourth year, in which a day is added to the month of February on account of the excess of the tropical year (365 d. 5 h. 48 m. 46 s.) above 365 days. But one day added every four years is equivalent to six hours each year, which is 11 m. 14 s. more than the excess of the real year. Hence, it is necessary to suppress the bissextile day at the end of every century which is not divisible by 400, while it is retained at the end of those which are divisible by 400.
Pertaining to leap year.
Source: Webster's dictionaryAll 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
Although there were exceptions, the first day of the bis sextum (February 24) was usually regarded as the intercalated or "bissextile" day since the 3rd century AD. Source: Internet
Hence, the year containing the doubled day was a bissextile (bis sextum, "twice sixth") year. Source: Internet
Mart., so if the days were numbered from the beginning of the month, it was named February 24 in common years, but the presence of the bissextum in a bissextile year immediately before a. d. VI Kal. Source: Internet
Mart. was the day after the bissextile day. Source: Internet
The 19th century chronologist Ideler argued that Celsus used the term "posterior" in a technical fashion to refer to the earlier of the two days, which requires the inscription to refer to the whole 48-hour day as the bissextile. Source: Internet