Tomorrow Saturday May 30th is the ancient Vigil of Pentecost. Before 1955, this day had its own special liturgy to prepare the faithful for the great Feast of Pentecost. It is not to be confused with an evening "anticipatory Mass for Sunday".
As some of you may recall, many major feasts in the traditional calendar had vigils the day prior that were also accompanied by its own Masses and abstinence or fasting - this included the Vigil of Ascension, Assumption, Nativity, and even the Vigil of St. Lawrence the Martyr.
The Vigil of Pentecost, it was very much similar to the Easter Vigil Mass, in some sense. According to the Facebook page Restore the '54, the Mass begins with deacon and subdeacon wear folded chasubles, penitential vestments, no altar candles are lit in the beginning, and 6 prophecies from the Old Testament (half of the twelve from the Easter Vigil) among other things.
Fortunately, you have an opportunity to watch this beautiful liturgy. Mater Ecclesiae Latin Mass Chapel in Berlin, NJ will live stream this Traditional Latin Mass:
Vigil of Pentecost Mass - Saturday May 30, 5:00pm Eastern
Restore the '54 Facebook page has an extended summary of the first part of the Mass (you don't need a Facebook account to review)