Candlemas marks the end of Christmastide.
Jewish religious rituals required that 40 days after the birth of a baby boy, he should be brought to the Temple to be presented to God. Luke 2: 25 - 40 tells the account of Mary and Joseph taking Jesus to the Temple. So on 2nd February, 40 days after Christmas, the Church celebrates Candlemas, or the Presentation in the Temple.
While the Holy Family was in the Temple, two elderly people, Simeon and Anna, saw the infant Jesus and proclaimed to everyone that he was God's promised Messiah - the one who would be a light to the world. Simeon's prayer as he held the child has become known as the Nunc dimittis, and forms part of the Church of England's service of Evening Prayer:
Lord, now lettest thou thy servant depart in peace according to thy word.
For mine eyes have seen thy salvation
which thou hast prepared before the face of all people;
to be a light to the Gentiles and to be the glory of thy people Israel.
Because of Simeon's assertion of Jesus becoming the light of the world, it became the custom for people to bring their 'lights' (candles) to church at Candlemas in order for them to be blessed.