Readings for Sundays
On most Sundays, we use the readings appointed for the day according to the Revised Common Lectionary, which can be found here:
Rarely, different readings may be selected, such as a transferred day (e.g readings for St. Luke's Day placed on nearest Sunday, etc.)
About the Lectionary
The Revised Common Lectionary or RCL is a set of readings that unfold over a 3 year cycle. The years are known as A, B, and C. Lectionary "years" begin on Advent, and we are currently in Year A. One of the many features of this cycle is that most Gospel readings come from Matthew (Year A), Mark (Year B), and Luke (Year C). These gospels are the three "synoptic" (with eye, aka eye witness) gospels of the N.T., and are placed in the canon of the N.T. in this order.
In addition to the 3 year cycle, there is a daily cycle, during which one can read the entire Bible in the course of three years.