Biblical holidays marking the seasons pf the agricultural calendar in Palestine were observed in conjunction with the sacrifical rites in the Temple. With the destruction of the Temple and the decentralization of religious authority, the holidays took on new significance. The author discusses the development of the sosio-religious base of the Sabbath, the developing theological character of Rosh HaShanah and Yom Kippur, the shifting symbolism of the Sukkah, the transformation of Chanukah from a national to a religious holiday, the evolution of Purim, the revision of the Passover Seder, the emergence of mourning aspects of the Sefirah period and the semi-fectival of Lag B'Omer, the substitution of new motif for Shavuot, the introduction of an additional festival day in the diaspora and the changing background of post-exilic fast days.