You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Galicia_(Spain)

Context:
Spanish was nonetheless the only official language in Galicia for more than four centuries. Over the many centuries of Castilian domination, Galician faded from day-to-day use in urban areas. The period since the re-establishment of democracy in Spain—in particular since the Lei de Normalización Lingüística ("Law of Linguistic Normalization", Ley 3/1983, 15 June 1983)—represents the first time since the introduction of mass education that a generation has attended school in Galician (Spanish is also still taught in Galician schools).

Question:
For how long was Spanish the official language of Galicia?

more than four centuries