[Solved] Please explain how this works

[CaliRay]

I was given a spreadsheet that tests whether or not a date, when reduced to a single number, equals a specific value, in this case 2, but I don't know enough about this to understand how it works or to then change it to test for a different reduced value. Example: 1966-03-22. The sum of the numbers is 29. 2+9 is 11 and 1+1 is 2. I need to test every date in the spreadsheet for values,when reduced to a single digit, are equal to 1,2,3 etc. thru 9.

I would appreciate an explanation of how this set of formulas determines that the reduced value of a date equals 2 and writes a 1 in column G indicating a true result.

Thank you for your review and help. Knowing how this works will enhance my currently limited knowledge of the functions used.

[Lupp]

Why should I trouble to "explain" an apparatus of formulae giving obviously wrong results?
You didn't even take the time to check the first row of the example for correctness of the result.

I checked and can tell you that all the example dates you gave have the continued cross-sum of 2.

How I got this result (beyond first checking a few examples in mind) you find in the attached demo. Random examples demonstrating the working are added. The formula I used is based on something you may have learned in school under the topic "How to test a number for being divisible by nine" which I found referred to as "casting-out-nines".
(If my demo doesn't work for you, you need to adapt the "YYYYMMDD" part to the letters used in your locale.)

The mentioned method for the calculation of continued cross-sums was more than once suggested in former threads in this forum, some of them also started in pursuit of some "numerological" topic. (The first post containing the formula I remember was by Zizi64 some years ago.)

See search.php?keywords=numerology e.g.

[Zizi64]

Test for reduced date equals 2 _ Zizi64.ods

(21.76 KiB) Downloaded 100 times

[CaliRay]

This solution from Zizi64 is easy to understand and easy to find all reduced values. I am grateful to all who helped get to this point.

[Lupp]

@Zizi64:
See also new attachment.

toZizi64ContinuedCrossSumForDates.ods

(50.12 KiB) Downloaded 95 times

[CaliRay]

Reducing a date yyyy,mm,dd to a single digit is solved but there's another step to do and that is to identify all dates within specific ranges that reduce to a specific number of 1,2,3... thru 9. The attached spreadsheet solves for dates within a range that reduce to the single digit 2 but I don't know how it works so I can modify it to solve for the other single digits.

[Zizi64]

@ Lupp:
Yes, always there are shorter and longer ways to the solution - I know that. Your solution is more elegant, and faster. (My resource-intensive "brute force" solution is good to check the results of your "tricky" solution. )

[CaliRay]

I've done a poor job of explaining the results I want to obtain. It is basically a 2 step process. First I check a list of dates and determine if the date, when reduced to a single digit results in a 1,2,3,4,5,6,7,8 or 9. Step 2 is to test each group of dates that are, say, a 1 and fall within a specific range of dates. For example I know that 1966-08-25 reduces to a 1 but does not fall between any of the date ranges I'm looking for which are 3-21:4-19, 5-21:6-20, 7-23:8-22, 9-23:10-22 or 11-22:12:22. The year is not important in step 2 but is used in step 1. I hope this is more clear. The spreadsheet I attached on Sun Oct 07, 2018 10:18 am above finds all dates that reduce to 2 and fall within the specified ranges but where I am lost is how do calculations in the spreadsheet know to test for 2? I need to understand how it works so I can modify it to also test for any other single digit number obtained in step 1.

I sure hope this is more clear. For the curious, I'm doing these tests as part of a study of numerology.

[Lupp]

For the curious, I'm doing these tests as part of a study of numerology.

Yes. It got obvious that your today's topics again were about so called numerology.

A few additional questions a curious man might ask:
Are there explicit hypotheses you want to test? What do you expect of such a sudy?

For additional studies in spreadsheetotechnics see attachment.
(I still was not sure what you were asking for beyond the already given answers.)

aoo95367ContinuedCrossSumAndEverything.ods

(121.01 KiB) Downloaded 96 times

[CaliRay]

Thanks for the explanations. Yes I do have a hypothesis I'm testing about "so called numerology". I haven't closed my mind to the possibility that there may be some validity in observations made by people observing human behavior and prejudices over the centuries and trying to find correlations in numbers associated with an individual. For me this is somewhat like the mystery of the Golden Ratio in nature. How did it come into existence? It's clearly observable and measurable.