In this dissertation, I study the observance of holy days among the peasantry in the early modern province of Savo, located on the eastern periphery of the Swedish kingdom (today Eastern Finland). I examine the practices, norms and meanings related to the observance of holy days both within and outside the Church, and analyse the changes and continuities in the post-reformation period. As the main sources of the study, I use district court records and visitation records mainly from the period 1639–1712. I analyse the cases with a micro-historical perspective and an anthropological approach. The lived religion of the peasantry was constituted especially through practices that were connected to annual holy days, both those officially celebrated and those officially denounced as superstition. The religious practice of the peasantry was shaped in the normative framework defined partly by Church and state and partly by the local communities. It was important for most peasants to attend church and take Communion on great holy days, even though in an agrarian area characterized by a scarce inhabitation and long distances, they were not able to make the long journey to church every Sunday. The practices and rituals related to the observance of holy days were increasingly concentrated on the church, but even the ecclesiastical and secular authorities had to bend in this process. The teachings of the Church were not understood as such, but merged in the popular mind with older ideas of the sacred and the relationship of people with the divine. To maintain its authority in the lives of the laity, the Church was forced to accept practices that were not in accordance with its doctrines. Nor was the Church able to replace the need for sacrificial practices and other rituals in the households. Traditional festivities and rituals officially condemned as superstition survived at least until the 18th century. To secure the continuity of life and a good relationship with the sacred, people held on to their traditions and celebrated holy days in a manner similar to that of their ancestors.