The Traditional Period of PassiontideBefore the revision of the liturgical calendar, however, Passiontide was the period of Lent that commemorates the increasing revelation of Christ's divinity and His movement toward Jerusalem. Holy Week was the second week of Passiontide, which began with the Fifth Sunday in Lent, which was known as Passion Sunday. (The Fifth Week of Lent was likewise known as Passion Week.) Thus Passion Sunday and Palm Sunday were (unlike today) separate celebrations.
The revised calendar is used in the Ordinary Form of the Mass (the Novus Ordus), which is the form of the Mass celebrated in most parishes.