Huh, you’re right. Calculators always use the decimal point rather than the comma. I’ve never even thought about that before.
Not all of them. On many Hewlett-Packard calculators, it is a user-configurable setting.
You do know that your comparison between commas and periods in numbers and in language is so invalid it’s painful, right?
I don’t know about Russian calculators, and my google-fu is not strong enough to find any online, but in Norway calculators use the decimal points because they’re not produced here.
My Norwegian standard keyboard on the other hand has a comma on the num-pad for entering the decimal separator, and the windows calulator has a comma as well. Calculators also use the ÷ sign, while my keypad and the windows calculator use a slash. Funnily enough, the slash isn’t used when writing a division on one line, for that we use a colon.
You mean the entire British Commonwealth? 
Except Canada… they seem to use both interchangeably
But strangely, the BBC’s in-house magazine is called Ariel. Ostensibly it is named after the character in The Tempest (“the spirit of the air”, and thus the essence of broadcasting, or something), but I have a sneaking suspicion that this explantion was made up after the fact to cover up a monumental cock-up. 
That brings another whole set of problems. I spent many years as a technical writer, and when we wrote a book using British (meaning “non-US”–sorry Martini and other Commonwealth residents, but this is how such spellings were known in our office) spellings, the Americans claimed we spelled words wrong. When we used American spellings, the rest of the Commonwealth claimed we were wrong. We couldn’t win!
IOW, we use them interchangeably because we have to if we expect to deal with the USA, our closest neighbour (neighbor?); and the rest of the English-speaking world. Your “calibre/caliber” is a good example; both versions look correct to me.
To address the OP, sort of… I recall one teacher I had back in the 1970s who claimed that some new (at the time) standard or convention stated that numbers were supposed to be written without commas, but with decimal points if required. Thus, one million would be written:
1 000 000.00
Was there such a standard or convention? If so, where did it come from? Or was the teacher trying to enforce a stylistic preference?
I believe that’s the S.I. (metric) standard.
So you laboured very hard at this job? Methinks this experience may have coloured your perceptions.
I don’t know whether that’s an international standard, but that’s how it is usually done in Germany today - just with a comma.
Germany is a decimal-comma country, but in some contexts with strong international influences the decimal point is common. Generally speaking the comma dominates in financial and non-technical office contexts but the point is found in many technical contexts (programming languages are an obvious example.) Although it is always called a comma, in writing you encounter both on a regular basis. Using the other one as a separator is just to likely to cause confusion.
I’m not a cheerleader for Excel, but it can format the separators any way you please. Just go to Tools…Options and in the International tab you can convert from one system to the other.
As far as dates- I agree that yyyy/mm/dd is the only logical way to do it.
Not sure if I’m being whooshed here, but yes–I labored hard at this job. It’s been rumored that it has colored my perceptions, but I feel pretty well centered. At any rate, I harbor no ill will against anybody who claimed to find a spelling error. No client ever canceled a contract, and so I collected a nice paycheck at the end of the day.
Now, want me to do it in British English? Part of my job for a few clients required the ability to flip back and forth just as quickly.
Oh, and thanks, acsenray, for the answer to my comma-less number question.