What is the difference between "Change time" and "Modify time"?

[Theodore Kilgore <kilgota banach math auburn edu>]

The question in the header refers, of course, to the options found under 
"Sort Order." Frankly, I can not tell the difference between the meanings 
of these two options -- unless perhaps I would take a deep dive into the 
source code. The man page does not seem to provide enlightenment on this 
point, either.

I have found out that the two options can sometimes act slightly 
differently, perhaps depending on distro or hardware, or something even 
more mysterious.

The usual occasion on which I would wish to sort files by date instead of 
by name occurs when I would connect to some repository and I want to get 
the most recent files in a certain directory. I have always used "modify 
time" to do the sorting, and it worked perfectly. But recently I tried to 
do this using an ARM netbook. The "modify time" then produced no change in 
the listing order of the files at all. But when I tried "change time" 
instead, I got the desired results. Now, as well as being built on ARM 
architecture, the netbook is also running a different distro from the rest 
of my machines. Thus, the important factor might possibly be the 
configuration of the distro, or it could be due to some quirk of the ARM 
architecture.

However, I still can not tell what the difference between "Modify time" 
and "Change time" was supposed to be in the first place, nor, for that 
matter, why both of these are separately listed as options when their 
names seem to mean the same thing with synonymous words. It seems to me to 
be something which is either redundant or confusing, or possibly both. 
Therefore, I thought it might be good to ask.

Theodore Kilgore