Thank you for posting. I’ve been missing those.
1) It was instituted less than 100 years ago in 1925
In the aftermath of the First World War, in the midst of the rise of Communism in Russia, and during the 16th centenary of the Council of Nicaea (325), Pope Pius XI instituted the feast in his 1925 encyclical Quas Primas, though its first celebration took place in 1926.
2) It was first celebrated on Halloween in 1926
It was originally supposed to be the last Sunday of October, just before the Feast of All Saints which, in 1926, just happened to be October 31st.
3) In 1969, Pope Paul VI revised the feast, giving it its current name and date
Pope Paul VI gave the feast its current full title (the Solemnity of Our Lord Jesus Christ King of the Universe) and moved it to the last Sunday of the liturgical year.
4) The feast was a response to the rise of secularization, atheism, and communism...
https://www.churchpop.com/2014/11/23/8-things-didnt-know-feast-christ-king/
Quas Primas ("in the first") as it is timed to Chanukah, the first night of candle lighting:
Quas primas (Latin: In the first) was an encyclical of Pope Pius XI. Promulgated on December 11, 1925, it introduced the Feast of Christ the King.
Friday, December 11, 1925
24 Kislev, 5686
The first feast day occurred in the following year on:
Sunday, October 31, 1926
23 Cheshvan, 5687
https://www.chabad.org/calendar/view/day.asp?tdate=10%2F31%2F1926
In 1969, Pope Paul VI revised the feast, giving it its current name and date...
The first re-timed date was the last "green" day, i.e. the last day of Ordinary Time:
Nov 22, 1970 (Sunday, 23 Cheshvan, thus the same Torah day-reading as above, when the first feast day occurred in 1926)