The Liturgical Calendar refers to the feasts and celebrations of the Christian Year. The Christian year starts with Advent at the end of November. The dates and themes for 2013 can be found here.
There exists a “Cycle of Prayer” for the year. This provides useful themes which can be used for assemblies and acts of collective worship. The Cycle of Prayer can be found here.
In addition the following websites may be useful:
The Liturgical Calendar of England & Wales including Saints days and Psalmter Weeks