"Rome's highest officials made a resolution to remain loyal to the republic and swore oaths to the Emperor on 1st January," said Professor Richard Alston, from the Department of Classics at Royal Holloway University.
"A grand ceremony marked the occasion, where the Roman legions would parade and sacrifices were made on the Capitoline Hill. This annual event renewed the bonds between citizens, the state and the gods," Alston said.
New Year's Day offered all Roman citizens an opportunity to reflect on the past and look to the year ahead.
"On 1 January, our Roman ancestors celebrated Janus, the god of new beginnings who had two faces - one looking into the past and another looking to the future," Alston added.
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"Janus represented doors and thresholds and the Romans named the month of January in his honour.
"Janus also symbolised the values of home, family, friendship and civilisation, and the doors of his temple were closed when Rome was at peace and thrown open in times of war, as if the god was no longer present.