AD 2015 was in the 21st century
The 21st century AD.
2015 is the 15th year of the 21st century.
1st century AD
It is the first century AD.
The 1st century AD.
It is the 18th century AD.
The first century AD.
It is the second century AD.
The 1st century AD.
The 1st century AD.
The first century AD.
The 3rd Century AD.