A spiritually enveloping, time-consuming, and value-creating set of activities, Aztecs centered their religion on powerful spiritual beings. Ceremony and time were fundamental parts of everyday life. From the smallest household to the largest city, rituals of offering to the gods took place every day as Aztecs sought water, food, the survival of human life, and balance in what they perceived to be a chaotic spiritual and material world. In their dynamic universe, deities and their human embodiments and priests and priestesses manifested great power. Ceremonies conducted for those beings, the offerings presented to them, and exchanged or distributed provide examples of the power and energy that offerings, including living humans, provided. Time-keeping focused on the notion of progressive ages, the idea of cyclical time, and two calendar systems. Their calendars used two ways of keeping track of days and months for ceremonies, agriculture, and war. Aztecs drew blood for human and plant fertility, purification, and to nourish and repay their debt to the creator deities. Yet the greatest offering human beings could give was to provide human lives, offering hearts and blood, though they did not do so in the numbers often suggested.