Question: "what is the first measurement of time mentioned?"  Context: "A year before Alfonso III "the Great" of Asturias death, three of Alfonso's sons rose in rebellion and forced him to abdicate, partitioning the kingdom among them. The eldest son, García, became king of León. The second son, Ordoño, reigned in Galicia, while the third, Fruela, received Asturias with Oviedo as his capital. Alfonso died in Zamora, probably in 910. His former realm would be reunited when first García died childless and León passed to Ordoño. He in turn died when his children were too young to ascend; Fruela became king of a reunited crown. His death the next year initiated a series of internecine struggles that led to unstable succession for over a century. It continued under that name[clarification needed] until incorporated into the Kingdom of Castile in 1230, after Ferdinand III became joint king of the two kingdoms. This was done to avoid dynastic feuds and to maintain the Christian Kingdoms strong enough to prevent complete Muslim take over of the Iberian Peninsula and to further the Reconquista of Iberia by Christian armies."  Answer:
The answer to this question is:
year