The Feast of Pentecost is the second of three compulsory pilgrimage feasts where the men travel to the Sanctuary in Jerusalem to present themselves before the Lord which occurs 50 days after the first fruits/barley sheaf waving.

THE SECOND OF THREE COMPULSORY PILGRIMAGE FEASTS:
Travel to the Sanctuary in Jerusalem required of all men, to present themselves before the Lord (Exo 23:14,17, Exo 34:22, Deut 16:16).
Exo 34:22, Lev 23:15-21, Acts 2:1, Acts 20:16, 1 Cor 16:8
Occurs 50 days after the day of first fruits / barley sheaf waving (16 Nisan), on or about the 6th day of the third month (Sivan).
A convocation / sabbath day. No servile work done. (Biblical Feast Days, 2016).

Reference: The Biblical Feast Days. Retrieved on Feb. 29, 2016. http://biblelight.net/feasts.html