One of the biggest problems with the average news media outlet is a great deal of ignorance on a very large number of topics.
A slightly lesser problem is that people misuse dictionaries. This is still a big problem but slightly less than the problem mentioned above.
The calendar which we use is a revision of the second major revision of a calendar which was first implemented at the beginning of the year which we call 45 BCE. At that time, it was known as the year 709.
A little more than five and a half centuries later, a man published a work in which he referred to the year in which he published it as being 525 years from the incarnation of Jesus. But there is no evidence as to how he came up with that number.
People in some countries started using that statement to number the years from that point onward. That was the first major revision.
But this calendar was not accurate over a long period of time due to the fact that the solar year includes a fractional day.
A little over a thousand years later another revision which introduced the day known as leap year day was introduced in some countries. Gradually over time and with minor occasional adjustments, this has become the "lingua franca" of calendars.
Those who developed this calendar did not use zero as a number. They treated zero as being merely an empty set, a null. Thus there was never a year zero in the numbering system. In modern times, some people have used the year 1 BCE as being equivalent to the year zero, but that messes up the numbering of the years which preceded 1 BCE.
Thus the calendar which we use began with January 1, 1 of the current calendar.
Ten years later, on January 1, 11 CE, the second decade began.
Ninety years after that, on January 1, 101 CE, the second century began.
Thus the current century began on January 1, 2001 and the current decade began on January 1, 2011 and will end on January 1, 2021.
Anyone who is a fan of 2001: A Space Odyssey should know that one of the main reason for the title is because 2001 is the first year of the 21st century. Arthur C. Clarke was not historically illiterate.