Whitsuntide

Just about all over now. Here it's still Whit Monday, a public holiday in quite a few European countries; but that's just a modern extension of Whit Sunday, a public holiday in a somewhat different list of European countries, and, under its Greek name of Pentecost, in  Greece (of course) and Iceland (?).
OE Hwīta Sunnandæg 'White Sunday', probably from the white robes of the newly-baptized at Pentecost (COD).
Greek pentēkostē (hēmera) 'fiftieth (day)'
(or "seventh Sunday after Easter"), when the Holy Spirit is said to have descended among the apostles.
Why fifty days? Well (I know it's not an answer, but) there is a Jewish harvest festival, on the fiftieth day after the second day of Passover (Lev.23:15-16). That again from COD.
Meanwhile in the Muslim world, there's been a pretty intense few days.
First there was Arafah Day, in the Emirates.
"In Islam, "Arafah" (عَرِفَة) refers to the Day of Arafah, which is the ninth day of the Islamic month of Dhul-Hijjah.
It is the most holy day of the Islamic year and a pivotal part of the Hajj pilgrimage, representing a time of repentance, forgiveness, and seeking divine mercy."
And more. This is from AI, who should know...
This day, I guess, forms part of the "Eid al-Adha Holiday" in Jordan (5-9 June), and is noted as "Hari Raya Haji (Feast of Sacrifice)" in Singapore (6 June) -- though the Malay expression really means Feast of Pilgrimage.
But "Feast of Sacrifice" is what Eid al-Adha means.
"Eid al-Adha[a] (Arabic: عيد الأضحى, romanized: ʿĪd al-ʾAḍḥā, lit. 'Feast of Sacrifice') is the second of the two main festivals in Islam alongside Eid al-Fitr. It falls on the 10th of Dhu al-Hijja, the twelfth and final month of the Islamic calendar."
Apparently commemorating Abraham's (almost) sacrifice of his son Isaac.
Not one of my favourite Bible stories. Hear Leonard Cohen's "Story of Isaac". He got fed up with blood-sacrifice and became a Buddhist.