Epiphany is the climax of the Advent/Christmas Season and the Twelve days of Christmas, which are usually counted from the evening of December 25th until the morning of January 6th, which is the Twelfth Day.
The term epiphany means "to show" or "to make known", "to reveal." In Western churches, it commemorates the coming of the wise men bringing gifts to visit the Christ child, who by so doing "reveal" Jesus to the world as Lord and King.
In western Christian tradition, January 6 is celebrated as Epiphany.
Because of differences in church calendars, mainly between the Eastern Orthodox and the western Catholic and Protestant traditions, both Christmas and Epiphany have been observed at different times in the past. Today, most of the Eastern Orthodox traditions follow the western church calendar. The exceptions are some Greek Orthodox Churches and related traditions (for example, Russian and Serbian Orthodox) that still follow the older calendar and celebrate Epiphany as the Theophany on January 19th.
What star is this, with beams so bright,
More lovely than the noonday light?
’Tis sent to announce a newborn King,
Glad tidings of our God to bring.
graphic: Epiphany Times Three by Kathrin Burleson Watercolor, 2007,