<Tr> <Td> 350 </Td> <Td> 18 January </Td> <Td> Magnentius, commander of the Jovians and Herculians, was acclaimed ruler of Rome by his legions . </Td> </Tr> <Tr> <Td> </Td> <Td> Constans was killed in Elne by followers of Magnentius . </Td> </Tr> <Tr> <Td> 3 June </Td> <Td> Constantius Chlorus's grandson Nepotianus entered Rome with a band of gladiators and there declared himself imperator . </Td> </Tr> <Tr> <Td> 30 June </Td> <Td> Marcellinus (magister officiorum), one of Magnentius's generals, entered Rome and executed Nepotianus . </Td> </Tr>

What were the three periods of roman history (in order)