The first century AD.
It is in the first century BC, which is different to the first century AD.
73 BC is in the 1st century BC. To convert years BC to centuries, you subtract the year from 1 and then divide by 100. Therefore, 73 BC falls in the period from 100 BC to 1 BC, which is the last century before the start of the AD era.
1st century AD
The first century AD.
The 3rd Century AD.
It is the first century AD.
The 1st century AD.
The 1st century AD.
It is the first century AD.
The 1st century AD.
It is the second century AD.
It is the 18th century AD.