What the 80s did to me
After a bit of twitter to and fro about when this current decade that we're in begins, I thought it was kind of interesting enough to blog about.
Is 2010 the beginning of our current decade or is 2011?
Decades are sets of 10 years, and as the AD counting of years begins with 1AD and not 0AD, the first set of 10 years since the beginning of counting them in the AD format is 1AD ending at the end of 10AD, so the second set of 10 years begins 11AD. By this reading the new decade begins this year, 2011.
There's a few ways of defining how long a year is, it can be a lunar year, seasonal, academic even. We currently use the Gregorian calendar which counts a year as having 365 days and 366 in a leap year. The Julian calendar gives a year 365.25 days hence the use of the Gregorian calendar to keep things tidy (and to do with trying to fix the equinoxes to near enough the same dates each year)giving us a leap year every 4 years. Astronomers use the Julian calendar err maybe it is more accurate or sumet.
We (Western world) began using the Gregorian calendar in the 1500s thanks to the then Pope helping us all out by standardising the calendar across the Holy Roman Empire. Kind of helps with trade I would imagine, and for calculating festivals like Easter and what not. Okay but because we'd all been going along with long winded non-standardised 'years' when the reformed calendar kicked in we had to cut out 10 or so days from the year to make up for the accumulated time-shift-error-y-stuffs. I mean, there were a lot of history ups and downs involved in setting the calendar and so what at first began with the Pope's edict and the need to drop 10 days actually meant that more than 10 days were eventually cut, here and there. Look, I found an equation that you can use to work out the difference between the Julian calendar and Gregorian calendar:
To make the working out of what a 'year' is and how to calculate where one begins and where one ends even more fiddly our year didn't always begin on the 1st of January. In Scotland they were a bit more sensible than England where I reside, and adopted 1st January as the beginning of a new year in 1600, but in England we really liked starting the new year on March 25th (known as Lady Day), so it took us until 1725 to catch up to our European buddies and move our new year new start to 1st January. So Charles I in his time was executed in 1648 but in history books he was executed in 1649 because of the calendar adjustments.
This is only relevant to the counting of where a decade begins because a decade is the counting of 10 years, so we've got to come to some kind of agreement about where a year begins and ends and how long it is before we can say how long 10 of them are. Especially as the English calendar change essentially means that we are in year 2010/11 right now (or is it 2011/12?).
Unless you are dead good at maths and logic problems I'd suggest that we choose our culturally accepted definition of a year to calculate decades, that is the year is counted by its name (1648, 1977 etc) and not by its strict constituent number of months or days. And that as we currently count our new year from 1st January that we count our current decades from then as well. This won't help for calculating sets of decades or 10 years in a mathematical sense from 1AD as there have been too many calendar changes to ignore since that date.
However the cultural concept of decades is a construct to allow us to reflect on the historical and social progression of time, and so in modern times we call decades by names, the 1910s, 1870s, 1650s, etc. It's a form of classifying them. In this way of counting decades the decade begins from ---0 and ends at ---9. The first decade was called the 0s and is 9 years long. The first century is 99 years long. In order to be able to talk about decades and centuries in a way that makes historical and cultural (but not mathematical) sense we must accept losing 1 year in the first decade.
So in the cultural sense our current decade is the 2010s and it began in 2010. In the mathematical sense I'm afraid I can't calculate when the decade began/ begins because trying to figure out from when to start the counting makes my head hurt. But it is kind of fun to think about nevertheless yes?
Is 2010 the beginning of our current decade or is 2011?
Decades are sets of 10 years, and as the AD counting of years begins with 1AD and not 0AD, the first set of 10 years since the beginning of counting them in the AD format is 1AD ending at the end of 10AD, so the second set of 10 years begins 11AD. By this reading the new decade begins this year, 2011.
There's a few ways of defining how long a year is, it can be a lunar year, seasonal, academic even. We currently use the Gregorian calendar which counts a year as having 365 days and 366 in a leap year. The Julian calendar gives a year 365.25 days hence the use of the Gregorian calendar to keep things tidy (and to do with trying to fix the equinoxes to near enough the same dates each year)giving us a leap year every 4 years. Astronomers use the Julian calendar err maybe it is more accurate or sumet.
We (Western world) began using the Gregorian calendar in the 1500s thanks to the then Pope helping us all out by standardising the calendar across the Holy Roman Empire. Kind of helps with trade I would imagine, and for calculating festivals like Easter and what not. Okay but because we'd all been going along with long winded non-standardised 'years' when the reformed calendar kicked in we had to cut out 10 or so days from the year to make up for the accumulated time-shift-error-y-stuffs. I mean, there were a lot of history ups and downs involved in setting the calendar and so what at first began with the Pope's edict and the need to drop 10 days actually meant that more than 10 days were eventually cut, here and there. Look, I found an equation that you can use to work out the difference between the Julian calendar and Gregorian calendar:
To make the working out of what a 'year' is and how to calculate where one begins and where one ends even more fiddly our year didn't always begin on the 1st of January. In Scotland they were a bit more sensible than England where I reside, and adopted 1st January as the beginning of a new year in 1600, but in England we really liked starting the new year on March 25th (known as Lady Day), so it took us until 1725 to catch up to our European buddies and move our new year new start to 1st January. So Charles I in his time was executed in 1648 but in history books he was executed in 1649 because of the calendar adjustments.
This is only relevant to the counting of where a decade begins because a decade is the counting of 10 years, so we've got to come to some kind of agreement about where a year begins and ends and how long it is before we can say how long 10 of them are. Especially as the English calendar change essentially means that we are in year 2010/11 right now (or is it 2011/12?).
Unless you are dead good at maths and logic problems I'd suggest that we choose our culturally accepted definition of a year to calculate decades, that is the year is counted by its name (1648, 1977 etc) and not by its strict constituent number of months or days. And that as we currently count our new year from 1st January that we count our current decades from then as well. This won't help for calculating sets of decades or 10 years in a mathematical sense from 1AD as there have been too many calendar changes to ignore since that date.
However the cultural concept of decades is a construct to allow us to reflect on the historical and social progression of time, and so in modern times we call decades by names, the 1910s, 1870s, 1650s, etc. It's a form of classifying them. In this way of counting decades the decade begins from ---0 and ends at ---9. The first decade was called the 0s and is 9 years long. The first century is 99 years long. In order to be able to talk about decades and centuries in a way that makes historical and cultural (but not mathematical) sense we must accept losing 1 year in the first decade.
So in the cultural sense our current decade is the 2010s and it began in 2010. In the mathematical sense I'm afraid I can't calculate when the decade began/ begins because trying to figure out from when to start the counting makes my head hurt. But it is kind of fun to think about nevertheless yes?