FESTIVALS or HOLYDAYS OF CHRISTIANITY
Christianity is a Semitic religion, which claims to have nearly 2.1 billion adherents all over the world. Christianity owes its name to Jesus Christ (Actual name is Eesa, peace be on him). The Bible is the sacred scripture of the Christians. Catholics believe that the pope is the successor to Saint Peter whom Jesus appointed as the first head of his church. The current pontiff or head of Christianity is FRANCIS, who is the 266th pope and succeeded Pope Benedict XVI in 2013. 
All Saints' Day (also known as All Hallows' Day or Hallowmas) is the day after All Hallows' Eve (Hallowe'en). It is a feast day celebrated on 1st November by Anglicans and Roman Catholics. to remember all saints and martyrs, known and unknown, throughout Christian history. As part of this day of obligation, Christian believers are required to attend church and try not to do any servile work.
Remembering saints and martyrs and dedicating a specific day to them each year has been a Christian tradition since the 4th century AD, but it wasn't until 609AD that Pope Boniface IV decided to remember all martyrs. Originally 13th May was designated as the Feast of All Holy Martyrs. Later, in 837AD, Pope Gregory IV extended the festival to remember all the saints, changed its name to Feast of All Saints and changed the date to 1st November. 
All Hallows' Eve falls on 31st October each year, and is the day before All Hallows' Day, also known as All Saints' Day in the Christian calendar. The Church traditionally held a vigil on All Hallows' Eve when worshippers would prepare themselves with prayers and fasting prior to the feast day itself.
The name derives from the Old English 'hallowed' meaning holy or sanctified and is now usually contracted to the more familiar word Hallowe'en.
A brief history of the festival
In the early 7th century Pope Boniface IV consecrated the Pantheon in Rome, formerly a temple to all the gods, as a church dedicated to Saint Mary and the Martyrs, and ordered that that date, 13th May, should be celebrated every year.
It became All Saints' Day, a day to honour all the saints, and later, at the behest of Pope Urban IV (d. 1264), a day specially to honour those saints who didn't have a festival day of their own.
In the 8th century, on 1st November, Pope Gregory III dedicated a chapel to all the saints in St. Peter's Basilica in Rome. Gregory IV then made the festival universal throughout the Church, and 1st November has subsequently become All Saints' Day for the western Church.
The Orthodox Church celebrates All Saints' Day on the first Sunday after Passover - a date closer to the original 13th May. 
The feast of the Annunciation marks the visit of the angel Gabriel to the Virgin Mary, during which he told her that she would be the mother of Jesus Christ. It is celebrated on 25 March each year. The festival has been celebrated since the 5th century CE. 
Christmas is marked on the 25 December (7 January for Orthodox Christians). Christmas is a Christian holy day that marks the birth of Jesus Christ.
The Gospels of Matthew and Luke give different accounts. It is from them that the nativity story is pieced together.
Both accounts tell us that Jesus was born to a woman called Mary who was engaged to Joseph, a carpenter. The Gospels state that Mary was a virgin when she became pregnant.
In Luke's account Mary was visited by an angel who brought the message that she would give birth to God's son. According to Matthew's account, Joseph was visited by an angel who persuaded him to marry Mary rather than send her away or expose her pregnancy. 
The first Christmas
The Gospels do not mention the date of Jesus' birth. It was not until the 4th century CE that Pope Julius I set 25th December as the date for Christmas. This was an attempt to Christianise the Pagan celebrations that already took place at this time of year. By 529, 25th December had become a civil holiday and by 567 the twelve days from 25th December to the Epiphany were public holidays. 
Easter commemorates the resurrection of Jesus Christ. It is the most important Christian festivals. On Good Friday, Jesus Christ was executed by crucifixion(based on Christian tradition). 
The Friday on which the Christian Church keeps the anniversary of the Crucifixion of Jesus Christ. The origin of the term Good is not clear. Some say it is from "God's Friday" (Gottes Freitag); others maintain that it is from the German Gute Freitag, and not specially English. Sometimes, too, the day was called Long Friday by the Anglo-Saxons. 
Candlemas commemorates the ritual purification of Mary, 40 days after the birth of her son Jesus. This day also marks the ritual presentation of the baby Jesus to God in the Temple at Jerusalem. On Candlemas night, many people place lighted candles in their windows at home.
Ritual purification stems back to a Jewish tradition that women were considered unclean after the birth of a child. For 40 days for a boy, and 60 days for a girl, women weren't allowed to worship in the temple. At the end of this time, women were brought to the Temple or Synagogue to be purified. After the ceremony women were allowed to take part in religious services again.
In pre-Christian times, it was the festival of light. This ancient festival marked the mid point of winter, half way between the winter solstice (shortest day) and the spring equinox. Some people lit candles to scare away evil spirits on the dark winter nights.