'Therefore that which shall be born of you shall be called the Son of God.' On which day also Christ suffered according to the flesh. The second solstice is on the eighth before the Kalends of July, when also St. John the Baptist was born, from which the day begins to decrease. The second equinox is on the eighth before the Kalends of October, on which day John the Baptist was conceived. And from this now the day becomes shorter than the night, until the Nativity of the Lord and Savior. From the eighth before the Kalends of April to the eighth before the Kalends of January, the days are counted as two hundred and seventy-one. Whence, according to the number of days, Christ our Lord was conceived on the Lord's day, the eighth before the Kalends of April, and Christ our Lord was born on the third feria, the thirteenth before the Kalends of January.
On the day on which he suffered there are completed 133 years and 3 months, which amount to 12,414 days. Hence, according to the number of his days, it stands that he was born on the fourth day of the week and suffered on the sixth: born on the eighth day before the Kalends of January, and suffered on the eighth day before the Kalends of April. From the time when Jesus Christ our Lord was baptized there are completed years, and the days are reckoned as ninety, which make 820, together with their leap-day additions; and thus he was baptized on the eighth before the Ides of January, on the fifth day of the week, and suffered, as I said above, on the eighth before the Kalends of April, on the sixth day of the week. With the leap-day additions they amount altogether to 12,415 days, and from the eighth before the Ides of January to the eighth before the Kalends of April there are ninety days. ARGUMENT 16. On the reckoning of the bissextile (leap-day). It must be believed that the bissextile is not made on account of that day on which, as some suppose, Joshua prayed for the sun to stand still;
for that day both existed and passed away. Rather it is called bissextile from this, that in each single month one 'point' accrues. Now one point is a quarter of an hour; four points make one hour, and twelve points complete three hours. Therefore in four years the threefold hours, which are twelve, make one day, which is added to February, since it then has the sixth day before the Kalends of March, so that on the following day it has it likewise. For example, if today is the sixth before the Kalends of March, that day is added in the completed fourth year; nonetheless on the morrow also let it be reckoned as the sixth before the Kalends of March. And it is therefore called bissextile (twice-sixth), because February twice has the sixth before the Kalends of March. In six days God made the world; on the seventh he rested.
Therefore, that it may be more fully understood, compute how many hours one day has, and divide them into seven parts, and however much remains, from that comes the bissextile. First compute the days, three hundred, how many hours they have: ten times three hundred is three thousand. Again you make: twice three hundred is six hundred; so in three hundred days there are 3,600 hours. Again you make: ten times sixty is six hundred, and twice sixty is one hundred and twenty. Therefore in sixty days there are 720 hours. Again you make: ten times five is fifty, and twice five is ten. Behold, in five days you have sixty hours. Together, in the whole year of 365 days there are 4,380 hours, and as many again in the night; together for the days and nights of the whole year there are 8,760 hours. Divide these into seven parts. First you make:
seven times one thousand is seven thousand, with 760 remaining. Likewise you make: seven times two hundred is fourteen hundred, with 360 remaining. Likewise you make: seven times fifty is three hundred and fifty, with ten remaining. Likewise you make: seven times one is seven, with three remaining. These three hours make, in four years, one day.