Determining whether we are currently in the 20th or 21st century can be a bit confusing, as there are different ways to measure and mark the passage of time. We are currently in the 21st century.
To understand why, it’s important to first understand how we measure time. The most commonly used calendar system today is the Gregorian calendar, which was introduced in 1582 by Pope Gregory XIII as a reform of the Julian calendar. This calendar divides time into years, months, weeks, and days, and each year is identified by a number.
The Gregorian calendar starts counting years from the birth of Jesus Christ, with the year of his birth designated as “1 AD” (Anno Domini, meaning “in the year of our Lord” in Latin). However, there was no “year zero” between 1 BC (Before Christ) and 1 AD, so the year before 1 AD is designated as “1 BC”. This means that there are 1,999 years between the start of the Gregorian calendar and the end of the 20th century.
The 20th century, therefore, includes all of the years from 1901 to 2000, while the 21st century includes all of the years from 2001 to 2100. So, technically speaking, we entered the 21st century on January 1, 2001, and we are currently in the 22nd year of the 21st century.
However, there are other ways to measure time that might lead to different conclusions about whether we are in the 20th or 21st century. For example, some people might argue that we are still in the 20th century because we have not yet completed 100 years of the 21st century. This argument is based on the fact that the “th” century is traditionally considered to refer to the period from year “01” to year “00”, so the 20th century would be the years from 1901 to 2000, and the 21st century would be the years from 2001 to 2100.
However, this argument ignores the fact that we use the numbering system established by the Gregorian calendar, which starts counting from the year “1” and includes both the first and last years of each century. It also ignores the fact that the convention of referring to centuries by their ordinal number (e.g. 20th, 21st) is based on the same numbering system.
Furthermore, there is a more compelling argument for considering the 21st century to have begun in 2001: the turn of the millennium. The year 2000 was widely celebrated as the end of the 20th century and the start of the new millennium, but this was actually incorrect according to the Gregorian calendar. As we noted earlier, there was no “year zero”, which means that the first millennium actually ended on December 31, 1000 AD, and the second millennium ended on December 31, 2000 AD.
We are in the 21st century. This is based on the Gregorian calendar, which starts counting from the year “1” and includes both the first and last years of each century, as well as the convention of referring to centuries by their ordinal number. While other arguments may be made based on different ways of measuring time, the turn of the millennium in 2001 is a compelling reason to consider the 21st century to have begun in that year.
