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Leap Year Error on the Julian-Roman-Actual-1 Calendar

Which years from 45 B.C. and later were leap years?

When Julius Caesar reformed the calendar into the modern-day calendar, he ordered that every four years, an extra 24 hours is inserted into it by method of expanding VI Kal. Mart. (Feb 24 on the modern day calendar) to 48 hours by doubling it. The "leap" 24-hour period was inserted between the last second of VII Kal. Mart. (Feb 23) ended and the first second of VI Kal. Mart (Feb 24), and calling it a 48-hour VI Kal. Mart. day called Bissextile, making February technically a 29-day length month consisting of 27 days of 24 hours each and one day of 48 hours. Later on, the "leap" 24-hour period became known as (bis) VI Kal. Mart or Bissextile Day (not Bissextile, which refers to the duo of two VI Kal. Mart.'s).

Also note that Terminalia Day, Feb 23 or VII Kal. Mart., was the last day of the old Roman year (not the civil year), whence some derive its name, which is also a meaning of terminal, or terminate the old year. Regifugium was on Feb 24 (Feb 25 in leap years) or VI Kal. Mart. In the old Roman calendar, an intercalary month was occasionally inserted. With the then-new Julian calendar, an intercalary day between Terminalia and Regifugium was inserted so that the calendar would slow down a day every four years and all of the festivals beginning with Regifugium through early Martius (March) would be grouped together.

What actually happened after Julius Caesar was assassinated in 44 B.C.E. was a leap year mess ans the pontifices initially added the "leap" 24-hour period every three instead of four years that Julius stated. The problem was probably the fact that people counted inclusively from four to one, starting at four on the leap year, then counting three, two, one, and landing on the year three years later that the pontifices would place a "leap" 24-hour period in, making the calendar slow down. By 8 B.C.E., the calendar was three days slow as too many "leaps" in a short period of time were inserted. Twelve intercalary or "leap" days were inserted in the length of time where only nine were really needed.

Julius intended for 45 B.C.E. to not be a leap year, and so the first intercalation according to him should be 41 B.C.E. Also note that the proleptic Julian-Roman-1 calendar year 45 B.C.E. does have an intercalary day in keeping with the leap every four years rule. If you want to see how the calendars the Romans used line up with the proleptic Julian-Roman-1 calendar, check out Chris Bennett's Roman Date Conversion Table in HTML. Note that the 46 B.C.E. Republican-Transitional calendar began on what he lists as October 12, 47 B.C.E. Julian-Roman-1 calendar. 45 B.C.E. Julian-Roman-Actual-1 calendar began on Dec 31, 46 B.C.E. Julian-Roman-1 calendar. 44 B.C.E. Julian-Roman-Actual-1 calendar began on Dec 30, 45 B.C.E. Julian-Roman-1 calendar. It goes on and on.

The intended years for the intercalary days should have been (skipping 45 B.C.E.) 41 B.C.E. (1st), 37 B.C.E. (2nd), 33 B.C.E. (3rd), 29 B.C.E. (4th), 25 B.C.E. (5th), 21 B.C.E. (6th), 17 B.C.E. (7th), 13 B.C.E. (8th), 09 B.C.E. (9th), 05 B.C.E. (10th), 01 B.C.E. (11th), 04 C.E. (12th), 08 C.E. (13th)

According to scholar Scalinger, the leap years were all in B.C.E.: 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12 and 9. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 2, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 4 C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 8 C.E.

Scalinger's theory of leap year placements might be correct but other scholars give other patterns such as:

Christmann: 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13 and 10, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 2, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 4 C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 8 C.E.

Bunting: 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15 and 12, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 1, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 1 B.C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 4 C.E.

Harriot: 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13 and 10, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 1, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 1 B.C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 4 C.E.

Kepler: 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13 and 10, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 2, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 4 C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 8 C.E.

Ideler: 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12 and 9, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 1, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 4 C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 8 C.E.

Matzat: 44, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14 and 11, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 1, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 1 B.C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 4 C.E.

Soltau: 45, 41, 38, 35, 32, 29, 26, 21, 20, 17, 14 and 11, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to January 2, 45 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 4 C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 8 C.E.

Bennett: 44, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14, 11 and 8, all in B.C.E. The first Julian Day, January 1, 45 B.C.E. Julian-Roman-Actual-1, mapped to December 31, 46 B.C.E. on the proleptic Julian-Roman-1 calendar. The first aligned day was on Feb 25 1 B.C.E. on the proleptic Julian-Roman-1 calendar. The Quadriennial leap year resumed on 4 C.E.

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