HWC Tutorial - Page 5 - Julian Calendar

Gregorian vs. Julian Calendar

The Gregorian calendar was introduced by Pope Gregory XIII in 1582, and was first used as of October 15 (Gregorian) of that year, but only in a few places. The British Empire (including her American colonies) adopted the new calendar as of September 14, 1752. (By now you should be able to find the weekdays of those two Gregorian dates. I'll tell you the answers at the end of this page.)

Before the Gregorian calendar was introduced, European countries and their empires used the Julian calendar, invented by Julius Caesar and implemented by the Roman Empire from 45 BCE onward. But due to misapplication of the leap year rule in its first few decades of use, we cannot start our system any earlier than March 1, 4 CE. That year may or may not have been a leap year (scholars disagree), but year 8 CE was certainly a leap year. And so the calendar can be traced back in a continuous system to March 1, 4 CE, the day following the last date of uncertainty.

In its outward appearance, the Julian calendar looks identical to the Gregorian. It has the same twelve months of the same lengths, running against the same seven weekdays. But the leap year rule is very slightly different, and the two calendars have been anywhere from 10 to 13 days apart from each other ever since the Gregorian calendar began, and they will continue to diverge as future centuries roll by. So at any time, the date in the Gregorian calendar is a bit in advance of the date simultaneously being observed in the Julian calendar.

The Julian calendar's leap years occur every four years without exception. Even the multiples of 100 are leap years, every time. This means that every Julian century is the same size, being one day larger than the "common centuries" we have been counting in the Gregorian calendar. So we only need to move back 1 weekday per century.

Using HWC with the Julian Calendar

To adjust our system to the Julian calendar, only three points of difference need to be considered:

• Start on the palm in the highest year which is a multiple of 700 (year 000 acts as a multiple of 700 in this context).
• To add 100 years, move back 1 position, until you reach the target century (no limit).
• If your target year is a multiple of 4, it is always a leap year even if it is a multiple of 100. (On the Gregorian Calendar, multiples of 100 are usually but not always common years. We saw the Gregorian leap year rule when we considered the months on page 3.)

If you wanted to, you could start on the palm at 000 (year "zero hundred"), then count off centuries one position at a time counter-clockwise until you reach the target century. But you'd be returning to the palm at every multiple of 700.

Once you've found the target Julian century, proceed through the years using the Dozens, Quads, and Singles just as before, pick the Doomsday entry date for the target month, and count your way to the target day, just as you would with a Gregorian date.

For the Julian calendar, all century limits are lifted, and you may cross the century at will using Dozens and Quads, though you shouldn't have to. But you still may not add more than three Singles after the last Quad, since that is a leap year limitation, not a century limitation.

(To answer the questions raised in the first paragraph of this section, Gregorian date October 15, 1582, was a Friday, while Gregorian date September 14, 1752, was a Thursday. They were immediately preceded by Julian dates Thursday, October 4, 1582, and Wednesday, September 2, 1752, respectively in their respective countries of use.)

Julian Example: October 12, 1492, Columbus' first landing in America

• Start 1400 = palm
• (No need to add Centuries)
• '12, '24, '36, '48, '60, '72, '84 = forward 1 seven times (palm)
• '88, '92 = back 2 twice (middle)
• (No need to add Singles)
• October 10 = no move (middle)
• 11, 12 = forward 1 twice (pinkie)
• Pinkie = Friday