The Spanish era or Era of the Caesars refers to the dating system used in Hispania until the fourteenth century and the adoption of Anno Domini. It began with year one in what is 38 BC, probably the date of a new tax imposed by the Romans on the subdued population of Iberia. Whatever the case, the date signifies the beginning of the Pax Romana in Hispania. To convert from a date in the Spanish era to the corresponding year in the Christian era, just subtract thirty eight years.