In Western Christianity, The Most Holy Trinity, also known as Trinity Sunday, is the first Sunday after Pentecost in the Western Christian liturgical calendar (and the Sunday of Pentecost in Eastern Christianity) which celebrates the Christian doctrine of the Trinity, the three Persons of God: the Father, the Son, and the Holy Spirit
This day is traditionally observed as a Solemnity, which includes reciting the Apostle's Creed and the Gloria.
Here are some ways you can observe this day according to Western Christian tradition: