The day the Magi came to the Christ-Child and offered their gifts of gold, frankincense, myrrh, in recognition of His Kingship, both before and after His death.
In this action was prefigured the welcoming of the Gentiles (non-Jews) into the bosom of the Church by Ss. Peter and Paul, for the Magi were Zoroastrians.
Would any of us us be here if the Magi had decided to ignore the star and not journey to see the Christ-Child?
Out of all of the customs that have arisen in celebration of the Epiphany, my personal favorite is the custom of eating cake. Known by various names in many countries, the cake is generally ring-shaped and incorporates a crown of some sort. Why is it my favorite? Cake. Why else?
There is also the custom, observed in such places as Poland and here in Canada, of writing with blessed chalk 20 + C + M + B + 19 over the main doorway of a residence. The initials stands for what are believed to be the proper names of the Three Magi: Caspar, Melchior, and Balthasar. It is a invocation of God's blessing upon a household to bless it and keep it throughout the calendar year.
Today, also, the Church announces the dates of the movable feasts for the year after Mass. This practice has largely fallen into disuse due to the advent of readily accessible calendars. But, when that wasn't the case, it used to be done. The Old Rite dictates that this be done by the deacon, while this can be done by the cantor or another layperson in the Novus Ordo. While I have never seen this done, I am told it is quite something.
Have a blessed Epiphany, and may God's blessing be upon you throughout the year to come.