Historical clue formulations

• Roman emperor before Hadrian — 2020-01-19
• Roman emperor born in Spain — 2012-05-22
• A tall Roman column is named after him — 2009-11-06
• Emperor before Hadrian — 2008-07-18
• Hadrian's predecessor — 2008-01-23
• Nerva's successor — 1996-12-27