This discussion arose (well, for me at least) when I was confronted with one of the definitions used for defining centuries. This definition is relevant for defining community tags on specific centuries.
The two different viewpoints
The two viewpoints are very concisely set out on this Wikipedia page
I will briefly point out the differences:
View point 1: Strict usage, the first century started in 1 AD, therefore every century starts in '01 and ends at the end of '00
View point 2: Usage as defined in ISO 8601, which defines centuries as starting in '00 and ending at the end of '99
I am asking for community opinions on which definition should be followed within the ELU community. An example which would depend on this definition is the excerpt for tags relating to centuries, e.g. the 20th-century-language tag. Should this be stated as 1901-2000 or 1900-1999?
I would argue to follow the ISO 8601 standard. That way, decades are associated with centuries, so the first decade of this millennium (2000-2009) is entirely in the 21-st century, rather than being split over the 20th and 21st.
I would also like to point out that ISO 8601 is not just something programmers use, to that end I am citing the Oxford Living Dictionary, which acknowledges the use of ISO 8601 in practice:
Strictly speaking, centuries run from 01 to 100, meaning that the new century begins on the first day of the year 01 (i.e. 1 January 1901, 1 January 2001, etc.).
In practice and in popular perception, however, the new century is held to begin when the significant digits in the date change, e.g. on 1 January 2000, when 1999 became 2000. Since the 1st century ran from the year 1 to the year 100, the ordinal number (i.e. second, third, fourth, etc.) used to denote the century will always be one digit higher than the corresponding cardinal digit(s). Thus, 1066 is a date in the 11th century, 1542 is a date in the 16th century, and so on
I would like to end with a quote from one of the more experienced users, because I think it is something that should be held in high regard, deciding democratically on one's own consensus:
"Due to the deliberately democratic philosophy behind Stack Exchange, a lot of the 'rules' are decided by community consensus. This is done in Meta. Even your post all rules in one place might become a 'rule' itself one day." -Lawrence