Probably 1100-1199 would be referred to as the 12th century. In our time, the 1900s were called the 20th Century.

The current century is the 21st: 2001 to 3000 inclusive.

The 20th century was 1901 to 2000 inclusive

The 19th century was 1801 to 1900 inclusive

The 18th century was 1701 to 1800 inclusive

The 17th century was 1601 to 1700 incusive . . . . and so on to:

The 1st century was 1 to 100 inclusive

The 1st century BC was 1 to 100 BC

The 2nd century BC was 101 to 200 BC . . . and so on back for millions of years to the creation of the planet.

The current century is the 21st: 2001 to 3000 inclusive.

The 20th century was 1901 to 2000 inclusive

The 19th century was 1801 to 1900 inclusive

The 18th century was 1701 to 1800 inclusive

The 17th century was 1601 to 1700 incusive . . . . and so on to:

The 1st century was 1 to 100 inclusive

The 1st century BC was 1 to 100 BC

The 2nd century BC was 101 to 200 BC . . . and so on back for millions of years to the creation of the planet.

The year 340 BC is classified as the 4th century BC.

20th century