I wish people would stop telling us that it’s the last X of the decade. It isn’t.
Let’s get this right. A decade is 10 years. This year is 2019, which ends in a 9. It is the ninth year of a ten year decade. There is one more whole year to go after this year before the decade comes to an end.
The first year was year 1, the second year 2 and so on. The tenth year was year 10. At the end of a year ending with a multiple of 10 we end a decade. The year 100 was the hundredth year, the end of a century. The end of 1999 was not the end of a century as we still had one year to go.
Not that ending a decade or century has any special meaning anyway…