the legendary founding of the city of Rome ( or ). Varro's date for this was 753BC but other writers used different dates, varying by several decades. Such dating was, however, never widespread. After the consuls waned in importance, most Roman dating was regnal or followed Diocletian's 15-year Indiction tax cycle. These cycles were not distinguished, however, so that "year 2 of the indiction" may refer to any of 298, 313, 328, &c. The Orthodox subjects of the Byzantine Empire used various Christian eras, including those based on Diocletian's persecutions, Christ's incarnation, and the supposed age of the world. The Romans did not have records of their early calendars but, like modern historians, assumed the year originally began in March on the basis of the names of the months following June. The consul M. Fulvius Nobilior (r.189BC) wrote a commentary on the calendar at the Temple of Hercules Musarum that claimed January had been named for Janus because the god faced both ways, suggesting it had been instituted as a first month. It was, however, usually said to have been instituted along with February, whose nature and festivals suggest it had originally been considered the last month of the year. The consuls' term of office—and thus the order of the years under the republic—seems to have changed several times. Their inaugurations were finally moved to 1January () in 153BC to allow Q. Fulvius Nobilior to attack Segeda in Spain during the Celtiberian Wars, before which they had occurred on 15March (). There is reason to believe the inauguration date had been 1May during the until 222BC and Livy mentions earlier inaugurations on 15May (), 1July (), 1August (), 1October (), and 15December (). Under the Julian calendar, the year began on 1January but years of the Indiction cycle began on 1September. In addition to Egypt's separate calendar, some provinces maintained their records using a local era. Africa dated its records sequentially from 39BC; Spain from AD38. This dating system continued as the Spanish era used in medieval Spain. Conversion to Julian or Gregorian dates The continuity of names from the Roman to the Gregorian calendar can lead to the mistaken belief that Roman dates correspond to Julian or Gregorian ones. In fact, the essentially complete list of Roman consuls allows general certainty of years back to the establishment of the republic but the uncertainty as to the end of lunar