What is the origin of popular customs associated with birthday celebrations?

"The various customs with which people today celebrate their birthdays have a long history. Their origins lie in the realm of magic and religion. The customs of offering congratulations, presenting gifts and celebrating—complete with lighted candles—in ancient times were meant to protect the birthday celebrant from the demons and to ensure his security for the coming year. . . . Down to the fourth century Christianity rejected the birthday celebration as a pagan custom."—Schwäbische Zeitung (magazine supplement Zeit und Welt), April 3/4, 1981, p. 4

"The Greeks believed that everyone had a protective spirit or daemon who attended his birth and watched over him in life. This spirit had a mystic relation with the god on whose birthday the individual was born. The Romans also subscribed to this idea. . . . This notion was carried down in human belief and is reflected in the guardian angel, the fairy godmother and the patron saint. . . . The custom of lighted candles on the cakes started with the Greeks. . . . Honey cakes round as the moon and lit with tapers were placed on the temple altars of [Artemis]. . . . Birthday candles, in folk belief, are endowed with special magic for granting wishes. . . . Lighted tapers and sacrificial fires have had a special mystic significance ever since man first set up altars to his gods. The birthday candles are thus an honor and tribute to the birthday child and bring good fortune. . . . Birthday greetings and wishes for happiness are an intrinsic part of this holiday. . . . Originally the idea was rooted in magic. . . . Birthday greetings have power for good or ill because one is closer to the spirit world on this day." —The Lore of Birthdays (New York, 1952), Ralph and Adelin Linton, pp. 8, 18-20

"It is thought that the large-scale celebration of birthdays in Europe began with the cult of Mithras ("a Hellenistic and Roman god"; "the central god of Mithraism") which originated in Persia but was spread by soldiers throughout the Roman Empire. Before this, such celebrations were not common;" -Wikipedia; Topic: "Birthday"; Heading: "History of celebration of birthdays in the West"

The Jews "regarded birthday celebrations as parts of idolatrous worship . . . , and this probably on account of the idolatrous rites with which they were observed in honor of those who were regarded as the patron gods of the day on which the party was born." -M'Clintock and Strong's Cyclopaedia (1882, Vol. I, p. 817)

"Birthday parties began years ago in Europe. People believed in good and evil spirits, sometimes called good and evil fairies. Everyone was afraid of these spirits, that they would cause harm to the birthday celebrant, and so he was surrounded by friends and relatives whose good wishes, and very presence, would protect him against the unknown dangers that the birthday held. Giving gifts brought even greater protection. Eating together provided a further safeguard and helped to bring the blessings of the good spirits. So the birthday party was originally intended to make a person safe from evil and to insure a good year to come."—Birthday Parties Around the World, 1967

The book also goes on to explain the origin of many birthday customs. For example: "The reason [for using candles] goes back to the early Greeks and Romans who thought that tapers or candles had magical qualities. They would offer prayers and make wishes to be carried up to the gods by the flames of candles. The gods would then send down their blessings and perhaps answer the prayers." —Birthday Parties Around the World, 1967