Happy Bissextile Day!
…the Original Leap Year Day
Although most of us will pursue our usual daily affairs on 24 February 2024 and not notice any difference, until just a few centuries ago our ancestors in many societies marked with caution their passage through what had to be one of the truly odd, and for some, ominous, days of the year—Bissextile Day. What is so odd, or even ominous, about this day? First of all is the fact that it does not occur every year, but only once every four years. While most of us are used to thinking of 29 February as the odd “Leap Year Day,” one has to go back only a few centuries to discover that on the calendars of many of our ancestors 29 February did not exist in any year—leap year or common—and that instead there was a strange-looking double occurrence of 24 February—hence bissextile, or “twice-sixth” day. (The calendars above from 1568 and 2024 illustrate the difference.)
Why “twice-sixth” day? It is a matter of understanding the Roman history of our calendar. In the Roman manner of naming calendar dates, 24 February is the sixth day to the beginning of March—hence the name VI Kalends Martius. In other words, if one begins with 1 March and counts backward, the sixth day is 24 February.[1] Since 1 March was understood by most people as the beginning of the year, 24 February is therefore the sixth day to the beginning of a new year. Since the number six was understood by many ancient peoples as somewhat incomplete and un-holy since it was just short of the holy number seven, the sixth day to the beginning of a new year was therefore viewed as the most un-lucky and un-holy day of the entire year. And with the need to add an extra day in every fourth year, the effect was doubled into a twice-sixth day that was viewed as the ultimate evil day in the calendar.
Today we make jokes and laugh along with anyone who has had the misfortune to be born on 29 February. Or perhaps it is good fortune, since they have a birthday only once every four years and therefore can jest that they age only one-fourth as quickly as the rest of us. But pity anyone in centuries past who had a birthday on 24 February—or especially anyone born on the bissextile day in a leap year. Such individuals were customarily told to celebrate on the day following, and many businesses were inevitably closed for the day. If the bissextile day fell on a Sunday, church services included extra prayers of repentance, as it often fell within the season of Lent regardless.
So which day is actually the bissextile day this year—24 or 25 February? In a common year of 365 days the sextile (“sixth”) day is 24 February—which means beginning with 1 March and counting backward inclusively to the sixth day. But in a leap year of 366 days the sextile day is 25 February since 29 February is included. Yet if we were using the calendars of a few centuries ago there would be no 29 February, but rather two consecutive occurrences of 24 February. So should the bissextile day be counted as the modern 24 February, since that is the seventh day counting backward from 1 March, and thus the second occurrence of the sixth day counting backward? Or should the bissextile day be counted as the modern 25 February, since that is the second occurrence of 24 February counting forward, and is the sixth day counting backward from 1 March? Such confusion! While evidence from previous centuries would appear to favor our modern date of 24 February, it can be argued both ways.
By the way, it might be worth remembering that before the Romans revised their calendar (ultimately named after their Emperor Julius) in 45 BC, February actually had thirty days. But since Julius’ birthday was in the fifth month of the year (“Quintilis”), after his death they decided to re-name the month in his honor. Furthermore, since Quintilis had only thirty days and was therefore shorter than some other months, the Roman Senate decided it was appropriate to add one day to the new month of Julius by taking a day that evil final month of February. Not to be outdone, however, in 8 BC the Senate decided to re-name the sixth month (“Sextilis”) after Julius’ nephew and successor Octavius—better known by his title “Augustus.” And since August had only thirty days, they again decided to add a day to the Emperor’s month by taking one more day from that evil final month of February. So even though February could expand to twenty-nine days in every fourth year, it was still shorter than all the rest.
Equally important to note, however, is the proclamation of Inter Gravissimas by Pope Gregory XIII on this date in 1582, which gave us the modern calendar utilized by most of the world today. While nothing is said in the statement itself relative to its proclamation on the bissextile, the clear implication is that the more important matter is the determination of the correct date for the celebration of Jesus’ resurrection.[2] So far from being the source of superstition and fear, the Christian faith is rather one of celebrating the redemptive act of God in human history through the sacrificial death and resurrection of his Son. And the fact that Gregory and his predecessors had enlisted the aid of astronomers and their painstaking research in making this calendrical change shows the overwhelmingly positive attitude and relationship of Christianity and natural science—contrary to the mistaken perception of antagonism by many moderns.[3]
[1] Bonnie Blackburn and Leofranc Holford-Strevens, The Oxford Companion to the Year: An exploration of calendar customs and time-reckoning (Oxford: Oxford University Press, 1999), 677ff.
[2] It is also interesting to note that the date given on the proclamation is 24 February 1581, since at that time the month of February was still viewed as the final month of the year. See Bill Spencer’s English translation of Inter Gravissimas at http://www.bluewaterarts.com/calendar/NewInterGravissimas.htm.
[3] For more on the background and development of Inter Gravissimas, see Steven L. Ware, When Was Jesus Really Born?: Early Christianity, the Calendar, and the Life of Jesus (Saint Louis: Concordia, 2013), 130ff.