The year 1990 belongs to the 20th century. The 20th century spans from the year 1901 to 2000. Therefore, any year from 1901 to 2000, including 1990, is part of that century.
18th centurery
The year 1785 belongs to the 18th century. The 18th century spans from the year 1701 to 1800. Therefore, any year within that range, including 1785, is classified as part of the 18th century.
Technically, it belongs to the 20th century. the 21st century didn't start until Jan. 1st 2001.
The years 7000 to 7999 belong to the 71st century. In the Gregorian calendar, centuries are counted by grouping years into sets of 100, so the year 7000 marks the beginning of the 71st century, which will end in the year 7999.
This was the 20th century (we are now in the 21st century).
18th centurery
The year 1785 belongs to the 18th century. The 18th century spans from the year 1701 to 1800. Therefore, any year within that range, including 1785, is classified as part of the 18th century.
If you were born in 1997, you would belong to the 20th century as the 21st century began in the year 2001.
Technically, it belongs to the 20th century. the 21st century didn't start until Jan. 1st 2001.
The year 721 was in the 8th century. Someone can determine what century a year is by adding one to whichever number is listed first in the year, and when the year got to 4 digits, it would go by the first 2 numbers.
1990 was in the 20th century.
It belongs to the 19th century, because the 1900's were the 20th century, and the first 100 years of the 2000's [which we are in right now] are the 21st century.
The 17th century.
20th century
This was the 20th century (we are now in the 21st century).
The tenth century spans the years from 901 - 1000. Note that not all people agree on this, and many believe that 1000 is the first year of the eleventh century; but if you count 100 years at once, starting at year 1, the situation is quite clear: the 1st. century is from 1-100, the 2nd century is from 101-200, etc.
The 7th century BC.