Living Christ’s Resurrection is the basis of the Divine Liturgy and underpins the entire structure of the liturgical order of the Church. The Church calendar is built around two cycles: movable and immovable feasts.
The first, movable feasts, relates to the most profound moments of divine revelation: time which the Greeks called kairos. The second, fixed or immovable feasts, relates to specific days in history, for example, the Nativity of Christ or the Annunciation. It never changes and so it is straightforward to understand. This time/cycle was regarded as chronos by the Greeks – the root of the word chronological.