May 06, 2017: "Remembering the Passion of Jesus of Nazareth".

The Plan of Salvation of

our Almighty only God 

YHVH-יחוח-YeHoVaH Creator

of the heavens and the earth

Shavuot: 

In the Bible, Shavuot is called the Festival of Weeks (Exodus 34:22, Deuteronomy 16:10;Exodus 23:16), and Day of the First Fruits (Numbers 28:26).

Shavuot, the plural of a word meaning "week" or "seven", alludes to the fact that this festival happens exactly seven weeks ( "a week of weeks") after Passover.

Pentecost:

The Christian Pentecost is based on the New Testament, where it refers to the descent of the Holy Spirit upon the Apostles and other followers of Jesus Christ, as described in the Acts of the Apostles 2:1–31. According to Luke 22:12–13, the descent of the Holy Spirit occurred while the Apostles were celebrating the Jewish day of Shavuot (Hebrew: שבועות‎‎, lit. "Weeks"), the Feast of Weeks, a prominent feast in the calendar of ancient Israel celebrating the giving of the Law to Moses at Sinai.

Subsequently, "Pentecost" may refer to the Pentecost of the New Testament and Shavuot of the Old Testament. Shavuot is a significant event shared by Jews and Christians but Christians do not commonly celebrate it as a separate holiday.

https://en.wikipedia.org/wiki/Pentecost