The Spanish era (Latin: Æra Hispanica), sometimes called the era of Caesar, was a calendar era (year numbering system) commonly used in the states of the Iberian Peninsula from the 5th century until the 15th, when it was phased out in favour of the Anno Domini (AD) system. The epoch (start date) of the Spanish era was 1 January 38 BC. To convert an Anno Domini date to the corresponding year in the Spanish era, add 38 to the Anno Domini year, such that Era 941 would be equivalent to AD 903. A date given in the Spanish era always uses the word era followed by a feminine ordinal number (when written out instead of given in Roman numerals). This contrasts with the AD system that uses the masculine anno (year): i.e., era millesima octava versus anno millesimo octavo.
The reasons behind the choice of 38 BC are unknown. It has been suggested that it may result from an Easter table that began with that year (rather than the Incarnation). Possibly 38 BC was the date of a new tax imposed by the Roman Republic on the subdued population of Iberia. Whatever the case, the date corresponds with the arrival of the Pax Romana in Iberia.
The Spanish era was used throughout the Visigothic Kingdom, which covered all of the Iberian Peninsula and the region of Septimania. It was even used in parts of North Africa. It continued in use in these regions but gradually fell away before the end of the Middle Ages. In al-Andalus under Muslim rule, the Spanish era was called the taʾrīkh al-ṣufr, "European era", from taʾrīkh (date, era, annals) and aṣfar (yellow, pale, red), a word which came to be applied to Greeks and by the Middle Ages to Europeans in general.
Official usage of the era ceased in different parts of the peninsula at different times: Catalonia dropped the era (as well as the French king's regnal year) in AD 1180, Aragon in 1349/1350, Valencia in 1358, Castile in 1382/1383, Portugal in 1420/1422 and Navarre in the early 15th century. While the year officially began on 1 January under the Spanish era, that was changed to 25 December when the Anno Domini system was adopted (while the Church used 11 January).
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