Pentecost, 49 Days After Easter (Western)

Pentecost falls forty nine days after Easter by the count this rule records, which reaches the fiftieth day counting Easter Sunday itself as the first, and the feast's very name preserves the count, Pentecost deriving from the Greek word for fiftieth. The occasion commemorated is the descent of the Holy Spirit on the apostles described in the second chapter of Acts, an event the text itself places on the Jewish festival of Shavuot, since the apostles are described gathered in Jerusalem for that pilgrimage festival when the event occurs.

The shared count, fifty days from Passover to Shavuot in the Hebrew calendar and fifty days from Easter to Pentecost in the Christian calendar, is not treated by historians of the liturgy as coincidental, since Easter's own dating is tied to Passover through the paschal narrative, and the early Christian Pentecost inherited both the numerical span and, initially, much of the Jewish festival's own name and position before developing its own distinct theological content. In English usage the day is also historically called Whitsunday, a name of disputed origin most commonly associated with the white garments traditionally worn by those baptized at the feast.