A fatwa translated into English in which Sh. Muhammad Saleh Al-Munajjed answers the following question, "I hope insha Allah this question reaches you in good health. My question is I have noticed when a non-Muslim asks about the age of Islam after prophethood, we - as Muslims - answer only with the years after Hijrah, my question is why do we always leave out the first 13 years of prophethood before Hijrah. I know the year of Hijrah was a great year yet we all know that prophethood started 13 years before this so when answering why don’t we mention this like now we are 1433 AH yet when answering why don’t we say Islam after prophethood is 1446 adding the 13 years before the period. Insha Allah, you can explain why we don’t add the first 13 years into our answer."