SundaySunday Observed by Christians as a day of rest and worship. Traditionally regarded as the first day of the week, the day on which Christ's Resurrection is believed to have taken place. For this reason it replaced the Jewish Sabbath in Christian practice. after PentecostPentecost Also called Whit Sunday. Seventh Sunday after Easter. The Jewish Feast of Weeks (harvest). Day when the Holy Spirit descended upon the disciples (Acts 2).. Celebrates God the FatherGod the Father Title given to the deity in the Judeo-Christian tradition, Son and Holy SpiritHoly Spirit Or 'Holy Ghost'. Third person of the Trinity..