The fifty days from the Sunday of the Resurrection to Pentecost Sunday are celebrated in joy and exultation as one feast day, indeed as one "great Sunday." These are the days above all others in which the Alleluia is sung.
The Sundays of this time of year are considered to be Sundays of Easter and are called, after Easter Sunday itself, the Second, Third, Fourth, Fifth, Sixth Sundays, and Ascension Sunday. This sacred period of fifty days concludes with Pentecost Sunday.
The first eight days of Easter Time constitute the Octave of Easter and are celebrated as Solemnities of the Lord.
On the fortieth day after Easter the Ascension of the Lord is celebrated, except where, not being observed as a Holyday of Obligation, it has been assigned to the Seventh Sunday of Easter (cf. no. 7).
The weekdays from the Ascension up to and including the Saturday before Pentecost prepare for the coming of the Holy Spirit, the Paraclete.