The UUA observes a diverse range of holidays reflecting its theologically pluralistic membership. Many UU congregations celebrate Christmas as a cultural and symbolic holiday — marking the birth of Jesus as a story of light coming into darkness — without necessarily affirming its traditional Christian theological content. Easter may be observed as a celebration of renewal and spring rather than as a doctrinal affirmation of physical resurrection.

Many UU congregations also observe solstices and equinoxes, reflecting the earth-centered spirituality that is one of the UUA's Six Sources. Flower Communion (a service celebrating diversity and community, created by Norbert Čapek in the 1920s) and Water Communion (in which members pour water from places that have meaning to them into a shared bowl) are distinctive UU rituals observed in many congregations. Jewish holidays may be incorporated in congregations with significant Jewish membership.

The UUA's pluralistic approach to the religious calendar reflects its commitment to drawing from the 'living tradition' of all human religious experience. No holiday is required, and individual congregations determine their own worship calendar. This eclectic approach to religious time is itself a theological statement: the sacred is not confined to any single tradition's calendar but can be found and celebrated across the fullness of human spiritual experience.