* Vulgar Latin: The ancestor of Spanish was Vulgar Latin, the everyday language spoken by Romans throughout the Roman Empire. This form of Latin evolved independently in different regions, eventually leading to the Romance languages.
* Castilian: By the 9th century, a distinct dialect of Vulgar Latin, later called Castilian, began to emerge in the region around Castile in the Iberian Peninsula. This dialect would become the basis for modern Spanish.
* 13th Century: Castilian began to gain widespread use and prestige, even becoming the language of the Spanish court in the 13th century.
* 15th Century: The unification of Spain under the Catholic Monarchs (1479) helped to solidify Castilian as the dominant language of the country. This period also saw the rise of Spanish literature, with authors like Cervantes contributing to the standardization of the language.
So, while we can't pinpoint a specific date, it's safe to say that Spanish has been a distinct language for at least 1,000 years.
Keep in mind that the evolution of languages is a continuous process, and Spanish continues to change and evolve today.