Christmas Price Index chose the items in the popular Christmas carol "The Twelve Days of Christmas" as its market basket: a partridge in a pear tree, two turtle doves, three French hens, four calling birds, five gold(en) rings, six geese, seven swans, eight maids, nine dancing ladies, ten leaping lords, eleven pipers, and twelve drummers. According to tradition, the purchasing of the items begins on December 26 and ends on January 6. PNC compiles both a "Christmas Price Index" and "The True Cost of Christmas." The "Christmas Price Index" is calculated by adding the cost of the items in the song. The "True
Twelve Days of Christmas Birth, inclusively counting the first day and last day. This day, or some day proximate to it, is also celebrated by the Pope and Roman Catholics as World Day of Peace. In many nations, e. g., the United States, the Solemnity of Epiphany is transferred to the first Sunday after 1 January, which can occur as early as 2 January. That solemnity, then, together with customary observances associated with it, usually occur within the Twelve Days of Christmas, even if these are considered to end on 5 January rather than 6 January. Other Roman Catholic liturgical feasts on the General