Holy Prophet travels to Madina (Hijra)

  "Narrated 'Urwa Ibn Az-Zubair: "Allah's Messenger met Az Zubair in a caravan of Muslim merchants who were returning from Sham. Az -Zubair provided Allah's Messenger and Abu Bakr with white clothes to wear. When the Muslims of Medina heard the new of the departure of Allah's Messenger from Mecca (towards Medina), they started going to the Harra every morning,. They would wait for him till the heat of the noon forced them to return. One day, after waiting for a long while, they returned home, and when they went into their houses, a Jew climbed up to the roof of one of the forts of his people to look for something, and he saw Allah's Messenger and his companions, dressed in white clothes, emerging out of the desert mirage.

 

  "The Jew could not help shouting at the top of his voice: 'O you Arabs! Here is your great man whom you have been waiting for!' So all the Muslims rushed to their arms and received Allah's Messenger on the summit of Harra. The Prophet turned with them to the right and alighted at the quarters of Bani Amr Ibn Auf, and this was on Monday in the month of Rabi ul Awal. Abu Bakr stood up, receiving the people, while Allah's Messenger sat down and kept silent. Some of the Ansar who came and had not seen Allah's Messenger before began greeting Abu Bakr, but when the sunshine fell on Allah's Messenger and Abu Bakr came forward and shaded him with his sheet, only then the people came to know Allah's Messenger. Allah's Messenger stayed with Bani Amr Ibn Auf for ten nights and established the mosque (Mosque of Quba) which was founded on piety. Allah's Messenger prayed in it and then mounted his she-camel and proceeded on, accompanied by the people till his she-camel knelt down at the place of the Mosque of Allah's Messenger at Medina. Some Muslims used to pray there in those days, and that place was a yard for drying dates belonging to Suhail and Sahl, the orphan boys who were under the guardianship of Asad In Zurara. When his she-camel knelt down, Allah's Messenger said: 'This place, Allah willing, will be our abiding place.' Allah's Messenger then called the two boys and told them to suggest a price for that yard so that he might take it as a mosque. The two boys said: 'No, but we will give it as a gift, O Allah's Messenger!' Allah's Messenger then built a mosque there. The Prophet himself started carrying unburned bricks for its building and while doing so, he was saying: 'This load is better than the load of Khaibar, for it is more pious in the Sight of Allah and purer and better rewardable.' He was also saying: 'O Allah! The actual reward is the reward in the Hereafter, so bestow Your Mercy on the Ansar and the Emigrants.' Thus the Prophet recited (by way of
proverb) the poem of some Muslim poet whose name is unknown to me." (Ibn Shibab said, 'In the hadiths, it does not occur that Allah's Messenger recited a complete poetic verse other than this one.') (Sahih Al-Bukhari)

Hijra - Islamic Calendar marks this date
 

Thus was accomplished the hijrah, or the flight of Muhammad as called in European annals, from which the Islamic calendar dates.