As of 2015, a good place to find the holy days in Year B is the Lectionary Page site. The site provides a comprehensive list for the holy days of obligation in Years A, B and C.
The list of holy days found on the Lectionary Page includes Advent, Christmas, the Epiphany, Lent, Easter and Pentecost. The links provided offer scripture verses that are used for each holy day service throughout that year.
In Catholic and various Christian faiths, the lectionaries are broken down into 3-year cycles. The annual cycle begins on the fist Sunday of the Advent season. In the year 2015, the lectionary for Year B is in place.
Holy days are to be observed by the faithful who should refrain from work or any type of activity that takes away from worshiping God. The people who follow faiths which observe holy days are required to attend service and observe the day of rest.
In Year B for the 2015 cycle, the lectionaries are based on the Gospel of Mark. The only exception to this is during the Easter season when the Gospel of John is followed. This is the same for Years A and C. Although falling on different days throughout the calendar year, the same holy days are observed every year.