What is Mission Sunday
In the Roman Catholic Church (and possibly others) the month of October is dedicated to prayer and support of the Church's missions in general, and especially missionary work which is done overseas. During the month, people are told about the Church's missionary activity abroad and asked to support it through prayer, sacrifice and financial contributions.This focus is centred around Mission Sunday which is observed on the 2nd to last Sunday in October each year. (This is often described as the 3rd Sunday - but in 2011 October has five Sundays, and it was on the 4th one.)
The changing dates for Easter means this falls on a different Sunday of Ordinary Time (ie in the liturgical calendar) each year. For example in 2014 and 2015 it is the 29th Sunday of Ordinary time, while in 2011 when it was on the 30th Sunday of Ordinary Time.
Because of this, the hymn suggestions are based on the general themes of evangelisation, mission and support for missionaries, rather than any particular Gospel cycle.