THE YEAR OF HIS NOBLE BIRTH
According to the most correct opinion of the scholars,
was born in the city of Makkah in the Year of the Elephant (in the year
570 or 571 CE), in the month of Rabee‘ul Awwal. 
THE DAY OF HIS NOBLE BIRTH
There is an agreement amongst the scholars that the Prophet was born on a Monday, and he said: "On that day I was born and on that day Revelation descended upon me."  However, as regards to the exact date of his birth, then the scholars have differed about this, although many scholars say he was born on the 12th of Rabee'ul Awwal.
Imaam an-Nawawee (d. 676H) - rahimahullaah - said:
"There is an agreement that he was born on a Monday
in Rabee‘ul Awwal. There is a difference of opinion whether that day was
the 2nd, 8th, 10th, or 12th of the month - and these are the four most
well known opinions concerning this." 
EVENTS AT THE TIME OF HIS NOBLE BIRTH
Certain miraculous events are reported to have
occurred at the time when the Prophet
was born. However, most of them are not authentically related, rather they
are da‘eef (weak) or mawdoo‘ (fabricated) and therefore cannot be relied
upon as decisive proof; such as the narration which states that some of
the galleries of Kisraa's palace broke up and collapsed, that the sacred
fire of the Magians died out, and that some of the churches on Lake Saawah
collapsed and sank down.  However, it is authentically
related that the Prophet
said: "I am a result of the supplication of my father Ibraaheem and
the glad tiding brought by ‘Eesaa (‘alayhimus salaam). And my mother
- when she bore me - saw a light shone out from her, which lit up the palaces
in Syria…" 
CELEBRATING THE DAY OF HIS NOBLE BIRTH
Imaam al-Faakihaanee (d. 734H) - rahimahullaah - said: 
"Celebrating the Mawlid has no basis in the Book or the Sunnah, nor is this action recorded from any of the scholars of this Ummah; those who are taken as Imaams to be followed and who adhere to the narrations. Rather it is an innovation which was introduced by the Battaaloon sect." 
As regards to the origin of this newly invented celebration, then some of the researching scholars have stated that the first person to innovate this practice was ‘Umar Ibn Muhammad al-Mulaa in the city of Mawsil in ‘Iraaq, during the fourth century as is mentioned by Imaam Abu Shaamah (d. 665H).  He was followed in his day by the likes of Abul-Khattaab ‘Umar Ibn Dihyaa: "who was employed in the west, then traveled to Syria, then he traveled to the city of Irbil in ‘Iraan, during the fourth century, where he founds its king, Mudthaffarud-Deen Ibn Zaynud Deen showing a keen interest in the milaad (birthday) of the Prophet . So he composed a book for him called 'at-Tanweer Fee Mawlidis Siraajil Muneer'; so he recited this to the king who then awarded him with one thousand deenaars." 
Imaam Maalik (d.179H) - rahimahullaah - said:
"Whosoever introduces into Islaam an innovation, and holds it to be something good, has indeed alleged that Muhammad has betrayed his message. Read the statement of Allaah - the Most Blessed, the Most High:
"This day I have perfected your Religion for you, completed my favour upon you and I have chosen for you Islaam as your Religion." [Surah Al-Ma'idah Verse 3]
So that which was not part of the Religion at that time, cannot be part of the Religion today. And the last part of this ummah cannot be rectified, except by that which rectified its first part." 
Thus, had the practice of celebrating milaadun-nabee
(the birthday of the prophet )
been something praiseworthy, then: "The salaf - may Allaah be pleased with
them - would have instituted it. For they were the ones having the greatest
honour and love or the Prophet
and a greater zeal for doing good. Indeed the most perfect expression of
love and honour for him
is by following him ,
obeying him ,
carrying out his
commands, upholding and reviving his
Sunnah - both inwardly and outwardly - and spreading his
message and striving in this with the heart and the hand and the tongue.
Such was the path of the Companions
and those who followed them in goodness." 
 Refer to at-Taareekh (p. 53) of Khaleefah Ibn Khayaat, as-Seerah (1/167) of Ibn Hishaam, also Tabaqaatul Kubraa (1/62) of Ibn Sa'ad.
 Related by Muslim (2/820) and Ahmad (5/297)
 Tahdheeb Seeratun Nabawiyyah (p. 20) of Imaam an-Nawawee.
 Munkar: Related by Imaam adh-Dhahabee in as-Seeratun Nabawiyyah (p. 11-14) who said: "This narration is munkar ghareeb (rejected and strange)."
 Related by al-Haakim in al-Mustadrak (2/600) and Ibn Katheer in al-Bidaayah wan-Nihaayah (1/229) who said: "Its chain of narrators is good and strong." Refer to as-Saheehah (no. 1545) of Shaykh al-Albaanee.
 Al-Mawrid Fee ‘Amalil Mawlid (p. 21-22)
 The Battaaloon: They are one of the deviated Baatiniyyah Shee'aa sects from the Faatimids - as al-Maqreezee says in al-Khatat (1//490).
 al-Baa'ith 'alaa Inkaaril Bida‘ wal-Hawaadith (p. 23-24), Ibnul Jawzee stated something similar in Miraatuz Zamaan (8/310).
 al-Bidaayah wan-Nihaayah (13/144-145) of al-Haafidh Ibn Katheer.
 Related by al-Qaadee 'Iyyaadh in ash-Shifaa fee Huqooqil Mustafaa (2/676).
Siraatil Mustaqeem (p. 295) of Shaykhul Islaam Ibn Taymiyyah.