The date of the yearly Pilgrimage to Mecca is the date when Islam was "perfected":
Let us look at the following Narration:
Narrated 'Umar bin Al-Khattab: "Once a Jew said to me, "O the chief of believers! There is a verse in your Holy Book Which is read by all of you (Muslims), and had it been revealed to us, we would have taken that day (on which it was revealed as a day of celebration." 'Umar bin Al-Khattab asked, "Which is that verse?" The Jew replied, "This day I have perfected your religion For you, completed My favor upon you, And have chosen for you Islam as your religion." (5:3) 'Umar replied,"No doubt, we know when and where this verse was revealed to the Prophet. It was Friday and the Prophet was standing at 'Arafat (i.e. the Day of Hajj)" (Translation of Sahih Bukhari, Belief, Volume 1, Book 2, Number 43)"
Islam was perfected and completed exactly in the same day and date as the yearly pilgrimage to Mecca, the "Hajj".
Allah, Islam, Quran, Muhammad questions and answers.
What is the place of Jews, Christians and non-Muslims in Islam.
The Mercy of Allah Almighty, and the Wisdom of the age of 40.