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:
Islamism

Context:
Islamists have asked the question, "If Islam is a way of life, how can we say that those who want to live by its principles in legal, social, political, economic, and political spheres of life are not Muslims, but Islamists and believe in Islamism, not [just] Islam?" Similarly, a writer for the International Crisis Group maintains that "the conception of 'political Islam'" is a creation of Americans to explain the Iranian Islamic Revolution and apolitical Islam was a historical fluke of the "short-lived era of the heyday of secular Arab nationalism between 1945 and 1970", and it is quietist/non-political Islam, not Islamism, that requires explanation.

Question:
When was the heyday of secular Arab nationalism?

between 1945 and 1970