AD means ano domini - "in the year of our Lord [Jesus Christ]". A century is 100 years. Therefore, the first century is years 1-100, the second century 101-200, etc.
St Florian was born in the 4 century about 250 AD in Cetium Austria
The 1st century AD.
It is the first century AD.
1st century AD
The 1st century AD.
It is the 18th century AD.
The first century AD.
The 1st century AD.
It is the first century AD.
The first century AD.
It is the second century AD.