I think "manger scenes" as they are typically erected should be considered as man's effort to visualize an event about which we have very limited information available, in that they likely compress events into a single scene. (Note that, traditionally, many folks don't add the Magi into the scene until January 6, the Feast of the Epiphany.) I am no biblical scholar, so please forgive me any mis-statements in what follows.
Luke speaks of the shepherds being informed by the angel that the birth occurred that very day and he says that they found the Baby in a manger. Matthew's account of the circumstances involving the Magi is less precisely fixed. His Gospel describes the birth as occuring during the time of Herod and, by inference from their meeting with Herod, the Magi's visit in the same reign - but does not make the two events simultaneous.
If you think about it, most of those traveling to Bethlehem for the census likely left shortly after and lodging would have been more readily available. One can surmise that Mary, Joseph, and the Baby had relocated to someplace more hospitable than the cave or stable, as soon as possible after Jesus' Birth. So, Matthew's description of the Magi visiting a "house", rather than the stable, might be explained in that respect, if it did not occur on the day of His Birth.
Certainly, if the date of Epiphany is considered to have any real-time significance, two weeks would have passed before the Magi's arrival. That it might have been even longer could be inferred from Herod's caution in ordering the killing of all infant boys aged two or younger, to be certain that he covered all possibilities.
We'll never know with complete certainty, as least not in this life, when the Magi came, just as we don't know precisely how many they were in number. Caspar/Gaspar, Melchior, and Balthazar are traditionally named, but folks have put other names to them. The Ethiopians speak of Hor, Basanater, and Karsudan; the Syrians nominate them as Larvandad, Hormisdas, and Gushnasaph; to the Armenians they were, anciently, Kagba, Badadilma, and Melkon.
More diverse than the names are the various numbers of them; they are depicted in various representations and traditions as being as few as 2 and as many as 14. The number 3 is most likely ascribed from the number of gifts they offered, although another early legend puts it to the fact that they represented all humanity in the three great races of Sem, Cham, and Japhet, with one being Caucasian, one Black, and the third Oriental.
Saint Bede the Venerable, in a work ascribed to him,
Collectanea et Flores, records the legendary names, as well as their appearances, and the gifts of each:
The first was called Melchior; he was an old man, with white hair and long beard; he offered gold to the Lord as to his King. The second, Gaspar by name, young, beardless, of yellow hue, offered to Jesus his gift of incense, the homage due to Divinity. The third, black complected, with heavy beard, was called Baltasar; the myrrh he held in his hands prefigured the death of the Son of Man.
Many cultures have folktales that tell of someone (other than the expected entourage of guards, servants,
etc.) who was supposed to travel with the Magi, but was prevented from doing so, by some circumstance or other, usually with consequences. Such "wannabe" Magi are usually associated thereafter with gift-giving, at either Christmas or Epiphany, in an endless search on their part for the Child.
Along this line, in Italy, one finds "La Befana", a kindly old witch. Legend says that she lived alone in the hills and noticed a bright star in the night sky. Later, 3 richly garbed men stopped and asked directions of her to Bethlehem. When she told them that she didn't know of any such a place, they invited her to join them in their search; she declined, as she was too busy.
After the Magi left, Befana suffered regrets about her choice, remembering her own child, who had died very young. She baked cakes and cookies for the Baby, took her broom (to help the Baby's mother clean), and set out to find the caravan. When she became lost and tired, angels appeared and gave her broom the power of flight, to speed her search. She roamed the world, hunting for the Baby and still does. Each year, on the eve of Epiphany, whenever Befana comes to a house where there is a child, she flies down the chimney to see if it might be the One she seeks. It never is, but she leaves a gift anyway.
Henry van Dyke, an early 20th century writer, crafted a short story, "The Other Wise Man", which related another legend. In it, Artaban, a fourth Magi, was late in arriving to meet the others, who had already left. By the time he came to Bethlehem, they and the Holy Family had left to flee Herod's wrath. Artaban wandered the earth for 33 years, searching and using his gifts (jewels) to benefit others. When he encountered Christ, face-to-face, on Golgotha, his fortune was gone and he wasn't able to ransom Him. As Christ died and earth was shaken by a quake, Artaban was struck by a stone falling from a building. As he lay dying, he heard a voice from Heaven, saying, "What you did for each of these, you did for Me."
Babushka, an elderly Russian folklore character, appears in two variants of such tales. One mirrors the Italian tale of the initially selfish and later repentant La Befana; the other is a variant on van Dyke's story, except that Babushka reaches the stable, sorrowing that she has given away all her gifts and is consoled to find that what she did for others, she did for the Baby.
Among both the "Saint Thomas Christians" of India (Malabarese and Malankarese Catholics and Orthodox) and the Chaldeans and Assyrians (where the Magi likely had their roots), legend says that the Magi encountered the Apostle Thomas some forty years later, when he arrived in their lands to evangelize. According to tradition, the three, all then elderly, having been brought together again by a reappearance of the Star, were converted, ordained, and elevated to the episcopate, dying shortly afterwards. According to the Archdiocese of Cologne's Proper of the Divine Office for the Feast of the Translation of the Holy Relics of the Sainted Magi, they were buried in "the city of Sewa in the Orient." The relics of the Magi were brought to Constantinople in the fifth century, transferred to Milan 100 years later, and taken to Cologne in 1164 by the Emperor Frederick Barbarossa.
The feasts of Saints Caspar, Melchior, and Balthazar are kept in the Coptic, Ethiopian, Eritrean, Chaldean, Assyrian, Malabarese, and Malankarese Churches on January 1, 6, and 11, respectively.
The magnificent Cathedral of Cologne was constructed specifically to provide a suitable repository for their relics and it is formally styled The Cathedral of the Three Kings.
The reliquary, largest in the Western world, can be seen here -
http://www.archaeology.org/online/reviews/threekings/jpegs/threekings.jpeg.
The Troparion of Christmas in the Liturgy of Saint John Chrysostom, used in Eastern Catholic Churches of the Byzantine Rite and in the Eastern Orthodox Churches, reads in part:
Your birth, O Christ our God, has shed upon the world the light of knowledge; for through it those who worshipped the stars have learned from a star to worship You, the Sun of Justice, and to recognize You as the Orient From On High. Glory be to You, O Lord!
There's a good discussion of traditions associated with the Magi in the online (early 20th century edition) of the Catholic Encyclopedia at Magi.
A recipe for Dreikönigskuchen or Three Kings Cake can be had here -
http://www.germanculture.com.ua/recipes/blxmas12.htm. I highly recommend it
The placement of the Magi in the stable or cave scene itself*, whether on Christmas Day or Epiphany, is almost certainly a convenience to human understanding. It offers the symbolic statement that Christ's birth was for all mankind, the poor and low-born shepherds and the rich, high-born, and educated Magi, as well as the choirs of Heaven. It would be much more difficult to convey that same understanding if the Magi's arrival were separated entirely from the visualization of Christmas morning.
*In iconography depicting the Nativity, the Magi are never present at the cave, but are always seen approaching at a distance.
me to repost my comments from an old thread on one of my favorite topics regardimg the Nativity - the visit of the Magi. (A subject on which I was versed early by the German nuns who taught us in grammar school - all devoted admirers of Father Francis X Weiser, SJ, who wrote extensively on German Christmas traditions.)
Whoa! I have seen photos of the reliquary before, but this is the first time I see this photo which shows part of the three skulls. Thanks for posting it.