Revised Julian Calendar - Arithmetic

Arithmetic

The following are Gregorian minus Revised Julian date differences, calculated for the beginning of March in each century year, which is where differences arise or disappear, until 8000 AD. These are exact arithmetic calculations, not depending on any astronomy. A negative difference means that the proleptic Revised Julian calendar was behind the proleptic Gregorian calendar. A positive difference means that the Revised Julian calendar will be ahead of the Gregorian calendar, which will first occur on 1 March 2800:

Gregorian minus Revised Julian date differences
Century
Difference
100
0
200
−1
300
−1
400
0
500
0
600
−1
700
−1
800
0
900
0
1000
0
Century
Difference
1100
−1
1200
0
1300
0
1400
0
1500
−1
1600
0
1700
0
1800
0
1900
0
2000
0
Century
Difference
2100
0
2200
0
2300
0
2400
0
2500
0
2600
0
2700
0
2800
+1
2900
0
3000
0
Century
Difference
3100
0
3200
+1
3300
0
3400
0
3500
0
3600
+1
3700
+1
3800
0
3900
0
4000
+1
Century
Difference
4100
+1
4200
0
4300
0
4400
+1
4500
+1
4600
+1
4700
0
4800
+1
4900
+1
5000
+1
Century
Difference
5100
0
5200
+1
5300
+1
5400
+1
5500
+1
5600
+1
5700
+1
5800
+1
5900
+1
6000
+1
Century
Difference
6100
+1
6200
+1
6300
+1
6400
+2
6500
+1
6600
+1
6700
+1
6800
+2
6900
+1
7000
+1
Century
Difference
7100
+1
7200
+2
7300
+2
7400
+1
7500
+1
7600
+2
7700
+2
7800
+1
7900
+1
8000
+2

In 900 Julian years there are 900⁄4 = 225 leap days. The Revised Julian leap rule omits seven of nine century leap years, leaving 225−7 = 218 leap days per 900-year cycle. Thus the calendar mean year is 365+218⁄900 days, but this is actually a double-cycle that reduces to 365+109⁄450 = 365.242 days, or exactly 365 days 5 hours 48 minutes 48 seconds, which is exactly 24 seconds shorter than the Gregorian mean year of 365.2425 days, so in the long term the average the Revised Julian pulls ahead of the Gregorian calendar by one day in 3600 years.

The number of days per Revised Julian cycle = 900 × 365 + 218 = 328,718 days. Taking mod 7 leaves a remainder of 5, so like the Julian calendar the Revised Julian calendar cycle does not contain a whole number of weeks. Therefore, a full repetition of the Revised Julian leap cycle with respect to the seven-day day weekly cycle is seven times longer.

Read more about this topic:  Revised Julian Calendar

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