ORDINARY TIME: After the feast of Pentecost which fell on May 20, the Church’s liturgical calendar changed from the Season of Easter to Ordinary Time. Many people might have missed this fact because the liturgical colour for Ordinary Time – green – is not used on the first two Sundays of this phase of the season. The Easter colour of white is continued because two solemnities – Holy Trinity and The Body and Blood of Christ – are celebrated on the Sundays following Pentecost.
The name “Ordinary Time” for that part of the church year outside the seasons of Advent, Christmas, Lent and Easter is perhaps rather an unfortunate term. The word “ordinary” commonly means something that is unexceptional or uninteresting. However, the word “ordinary” as used in “Ordinary Time” means that the Sundays after the seasons of Christmas and Easter are counted in order, using ordinal numbers.
It is best to think of Ordinary Time as one of the liturgical seasons – the longest season of the church year. Its liturgical colour of green points to our Christian hope and life, entering into the mystery of Christ in all its fullness.

Ordinary Time enables us to devote ourselves to exploring the mystery of Christ in all its aspects and to celebrate the presence of God in the ordinary patterns of human life.

(Ref. "Liturgy Brisbane")