According to my girlfriend, mathematically the “20s” have only begun since the start of this year as of 01/01/2021.
I’m open to the concept, as I googled it and it seems to be some kind of “school of thought” but I think she was doing a really bad example of explaining it to me, using examples such as the 1st floor of a building is the ground floor, technically. But that isn’t really mathematical, because in maths you begin with 0 then, for example, 0.1, 0.2, 0.3 etc, but I’m not that confident of my maths skills as I’ve never particularly been that good.
She also said because you go from 1BC to 1AD, there was no “Zero Before Christ” or “0 Anno Domini”, but I argued that that is just where we decided the consecutive years begin from with the Gregorian Calendar, and isn’t mathematical.
Am I fundamentally mistaking what she means by mathematical? It was kind of starting to make my head hurt as according to that math, somebody isn’t 10 years old until they’ve been alive for 11 years, which is what I said to her, and she said yes, then seemed confused herself. which is why I’m requesting an from you guys, as from googling the subject, I’ve found myself quite interested in this concept but I’m massively struggling to wrap my head around it.
Thanks 🙂
In: Mathematics
You’re not alone in this! There are actually huge divides in all kinds of different fields related to engineering and programming and math, about whether it makes more sense to start counting things from 0 or from 1 in this context or that. You’re quite right in saying that it’s a ‘school of thought’ thing, there often is no consensus on what these conventions should be, or which is more ‘mathematical’.
But if any of these conventions really are non-mathematical, I think the Gregorian convention is a pretty good candidate. Lots of places in math, we use the natural numbers starting from 1, and lost starting from zero, and some places we use the whole number line of integers… but I can’t think of anywhere in “real” math that we’d ever use a number line which has negative integers and positive integers but skips 0, which seems to be what the B.C./A.D. year numbering system does.
You might be amused to learn that these kinds of misunderstandings are broadly known as “fencepost errors”. They’re called this, because of a classic puzzle that goes something like “If you build a 30 meter fence with posts spaced 3 meters apart, how many posts do you need?” We often miss the answer to questions like this by 1, because we lost track of whether we count 0 or not.
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