The Day of Disaster, also the day of shame on mankind, when in daylight, a whole country was stolen from its people by invaders.

Palestinians have been mourning the loss of their homeland since 1948, but Nakba Day, an annual day of commemoration inaugurated by the Palestinian Authority, is a relatively new addition to the calendar.
"Nakba" is just the Arabic word for disaster. After 1948, with the definite article “al” (i.e., al-Nakba), it became the proper name for the displacement of hundreds of thousands of persons and the establishment of a Jewish state following the Israeli War of Independence.
Yet for decades, no day was singled out as a day of commemoration, though some Palestinian Israelis took advantage of the national holiday on Israeli Independence Day to visit their lost homes or deserted villages within Israel.
This would change in 1998. As Israelis were preparing an elaborate celebration for the nation's 50th anniversary, Palestinian Authority President Yasser Arafat decided that Palestinians should mark the 50th anniversary of the Nakba as well. He declared May 15, the day after Israeli independence in 1948, as Nakba Day.

https://www.haaretz.com/israel-news/2022-05-15/ty-article-magazine/a-brief-history-of-nakba-day/00000180-d635-d572-aba5-debd6f320000