As the source of all life and growth on Earth, the Sun is the Universal Savior and King of Heaven. It is the original "dying-and-rising god" seen in many religions including Christianity and Zoroastrianism, and its role as the governor of the seasons means that its myths are often personifications of these natural cycles. For example, the "solar Christ" was a very popular theory in the 19th and early 20th centuries, though it has since fallen out of favor among biblical scholars (however there does exist a persistent "mysticist" stream, represented by such writers as Acharya S.). The Sun was the first of the seven Ptolemaic 'planets' (from Gr. planetese, 'wanderer'), and was equated with gold, one of the seven metals of Egypt (presumably also of the Ptolemaic period). The Sun is man, summer, heat and dryness while the Moon is woman, winter, silver, coolness and moisture.
Dies Natalis Sol Invictus The vast majority of religious celebrations, no matter where in the world, tend to center on the times of the solstices (December 21 and June 22) and equinoxes (March 21 and September 22), as they are the major turning points in the solar year marking winter and summer, spring and autumn respectively. Most others center on the cross-quarters, or exact mid-points between these dates. The solstices are the extremes of light and darkness, and the equinoxes are their two balanced points in the year.
Consider the fact that Christmas (Dec.25) is a mere four days after the winter solstice, and has been such for some 900 years or so (i.e., since before the introduction of the Gregorian calendar in 1582, which likely caused the four-day shift). It has been proposed that this date was chosen to align with the Roman "Dies Natalis Sol Invictus" (literally "Nativity Day [of the] Unconquerable Sun"), however there are many who disagree with this theory - perhaps most notably the Church of England. That the major Christian celebrations are predominantly solar in nature can hardly be argued, though, as for example the birth of John the Baptist has been assigned to the other solstice.
The nativity of the Universal Savior is December 25th (technically 21st) because this is the longest night of the year: the "light of the world" (John 8:12) is but an infant; weak, low on the horizon. The Sun is at its 'youngest.' What often follows this birth is the archetypal Saturnine infanticide, in this case personified by Herod, who foresaw his own downfall with the omen of the Eastern Star. This star is most likely Venus, the Mother Goddess who may be recognized in the Holy Families of many civilizations, such as Egypt (Isis and Horus, or later Mary and Christ).
The Saturnine infanticide is also seen in the birth of Zeus to Kronos (Saturn), the latter having nearly eaten the former in order to retain his kingship; ultimately he failed, as is invariably the case. This concept represents the lower, material self attempting to conquer and devour the pure, higher aspirations of the spirit.
Agnus Dei and the Mithraic Tauroctony It is for reasons of fundamental as opposed to mere mythical correspondence that many scholars formerly equated Jesus with other solar deities - most frequently Mithras, Horus, Osiris and Dionysus. That each of these gods embody different cultural ideals is of little significance in the present context: Jesus, Dionysus and Mithras are all opposites: one a disciplined preacher of peace, the other a licentious alcoholic, still another a fierce warrior. Yet there are marked similarities between these deities and their lives, perhaps most emphatically between the Tauroctony (bull-slaying) of Mithras and the sacrifice of the Christian Agnus Dei (Lat., "Lamb of God;" i.e., Jesus).
Many have suggested that these two events have little in common apart from the fact that they both occur around the time of Easter, or the spring equinox. It has been argued that because Mithras slays a bull, while Christ is slain as a lamb, the two are completely different; yet turning to astrology one notes firstly that the Mithraic is inevitably the older, as Taurus (the Bull) governed the time of the spring equinox up until c.200BCE, when this event slipped into Aries, the Ram; and secondly that Agnus Dei upon the Cross at Easter must surely be the Sun in Aries 'crossing' the celestial equator into the season of rebirth, bringing about the cyclical "redemption of all life."
Further examples could be given, such as the fact that wine was a sacrament of Jesus, Mithras and Dionysus; that bread was of the former two; that Isis, mother of Horus, offered man wheat and grapes; etc.
The Baha'i symbol of the sun is one of infallibility and permanence. Most Baha'i symbols are based on nature analogies. But, most nature analogies lack permanence. For example seeds, plants, winds and waves all come and go. But, the sun remains stable. That's because the sun represents the truth. In the Baha'i faith, real spiritual truth is unchanging.