QMDJ works based on a battlefield maps we draw, to do that we use a number specific for the day(for hour school). We call it Ju or Structure/Strategy(or something similar) Number.
This numbers changes around every 5 days and there are 2 popular ways of counting them. One is Zhi Run, the other is Chai Bu.
So one question that sometimes come up is what is the difference between Chai Bu and Zhi Run count for the Ju number in QMDJ.
The idea here is that Chai Bu is simplified while Zhi Run was what was used originally, is in the old texts and sometimes is called "Imperial" for that reason.
Here is how they would fit if we try to apply them to the Solar Term(that is more related to Chai Bu as we will see below).
https://web.archive.org/web/20130918110413/http://www.fivearts.net/index.php/topic,4768.0.htmlDec -------------------------------- Feb -------------------------- Apr
(s,b) dd/mm ST01 1,7,4 -------- dd/mm ST05 9,6,3 -------- dd/mm ST09 5,2,8
(s,b) dd/mm ST02 2,8,5 -------- dd/mm ST06 1,7,4 -------- dd/mm ST10 4,1,7
(s,b) dd/mm ST03 3,9,6 -------- dd/mm ST07 3,9,6 -------- dd/mm ST11 5,2,8
(s,b) dd/mm ST04 8,5,2 -------- dd/mm ST08 4,1,7 -------- dd/mm ST12 6,3,9
(s,b) ----------------------------------------------------------------dd/mm Leap 6,3,9
Jun --------------------------------- Aug ------------------------- Oct
(s,b) dd/mm ST13 9,3,6 -------- dd/mm ST17 1,4,7 -------- dd/mm ST21 5,8,2
(s,b) dd/mm ST14 8,2,5 -------- dd/mm ST18 9,3,6 -------- dd/mm ST22 6,9,3
(s,b) dd/mm ST15 7,1,4 -------- dd/mm ST19 7,1,4 -------- dd/mm ST23 5,8,2
(s,b) dd/mm ST16 2,5,8 -------- dd/mm ST20 6,9,3 -------- dd/mm ST24 4,7,1
(s,b) ----------------------------------------------------------------dd/mm Leap 4,7,1
Dec
(s,b) dd/mm ST01 1,7,4
https://web.archive.org/web/20130918110413/http://www.fivearts.net/index.php/topic,4768.0.html
So why if the original approach,Zhi Run has so many legends and stories about it we can sometimes see materials/authors saying Chai Bu is better?
Well, for one it is very easy to calculate. We just look at the Solar Term and Yuan and set the number.
If we think logically about it, each Solar Term is 15 degrees of Suns longitude. Each Ju is around 5 days long. Basically Chai Bu would be 1 number for each 5 degrees of Sun longitude.
This is very connected to the Sun, so in a sense seems much simpler and potentially easy to calculate approach(at least if you know the position of the Sun).
Also gives it some connection to XKDG in first glance, although the small difference in degrees will make it meaningless a step later.
Zhi Run...
QMDJ in my humble view is different then many of the other systems. There is idea of cosmic origin there ,more then many of the others in the five arts. In the past I have looked at many western systems that have history of "arriving" in another way, not as human invention/exploration and one thing that usually comes up is - the more you manage to stay near what was given originally the better it will work.
Now, if we try the same approach with the 8 houses Feng Shui for example, it will be impossible to practice it in todays world. So it isn't for all systems, then again no one ever said 8 houses had such origin... So its just for the once that seem like they have been given in full form from somewhere else where they may know much better then us what they are calculating and doing, overall.
So back on Zhi Run... Zhi Run is the closest thing to what was given originally. In some years it will "insert" extra days before summer or winter solstice to make the count even(as logically 360 days have to fit into a year).
There are 2 problems I have heard for Zhi Run.
One is that there is insertion of extra days. In my view, once we understand it, that it is done in such a beautiful and symmetric way that for me its the other way around, this is a reason to think this count works better(if we use the 3 solstice method, as in my view that is Zhi Run in its original way).
Making it a advantage and not a problem. Also again gives indication of something that is beyond what most humans can calculate by themselves and make it fit as precise.
Another problem I have heard is that when Zhi Run was given calendar was different, so it was approximation. In Tang dynasty calendar was changed to fit into the longitude of the Sun, so Chai Bu works better now as we assume the Ju is suppose to fit to the longitude of the Sun as the Solar Terms and month branches are.
However that is very big misunderstanding of how it works in my humble view. Zhi Run doesn't use Solar Terms. People use it as it will make calculation easier, the 3 solstice method needs only the Day stem/branch and the solstice days.
So to clarify - if we use the 3 solstice method Zhi Run won't be using the Solar Term or month divisions in any way. So any changes in the calendar for the months won't matter at all. It is continuous stream of numbers from one solstice to the next, and Solar Terms or the months are used, so someone can get into it at a random point in the stream(as the whole circle is 360 that is easy to do). But while it is very capable of working with the Solar Terms, the real count is not based on that. Making Chai Bu a count that is fixing problem that doesn't really exist.
On to the big question... What works better.
I think its better to let everyone decide for themselves. And of course existence(the flow) has a way of making things work, so anything we use will have some validity, doesn't mean when we get deeper they will both work with the same accuracy. Try and see. : )