*1st Generation dance. A dance that developed in a traditional way – not ‘taught’ by a teacher or choreographer, but ‘learned’ by observing and imitating others in your “village”, where the village’s few dances were the only dances anyone knew. It usually is ‘generic’ – the dance pattern is fairly simple and not tied to any particular piece of music. The dance phrase may or may not match any musical phrase, but the music’s rhythm must be suitable for performing the footwork. This dance may have many variations, but they’re performed at the whim or inspiration of the leader or (sometimes) any other dancer so long as it doesn’t interfere with the flow of neighboring dancers. For more, click here, here, and here.
Djurdjevka (dyur-DYEF-kah) is a Serbian folk song (Oj devojko, dušo moja – the first line of the lyrics) that has a dance specific to it. For song lyrics, see https://folkdancefootnotes.org/music/djurdjevka-kolo-english-lyrics/
The song has slight variations in the melody. Also, some versions have a different, QS (3/4) rhythm. The first description of Djurdjevka the dance was in the first systematic study of Serbian dance, by the Janković sisters, published in 1934. Their description was of a Djurdjevka in 3/4, perhaps like the dance below.

Ron Houston, in the 1993 Folk Dance Problem Solver states “John Filcich says it originated in central Serbia as a dance to 3/4 rhythm music and spread to Vojvodina as a 2/4 dance. Cerainly in regions such as Bachka, Srem, and Banat, it’s 2/4. Certainly in central Serbia, it’s 3/4. But the steps indicate a northern, perhaps Romanian origin, and 3/4 music came to Serbia from Europe. What’s the real story? I don’t know.”
The dance, though pretty similar in terms of weight changes, has variations in terms of moving or not moving in space.
I can find no YouTubes of Serbians dancing Djurdjevka outside of stage settings. Even performances are hard to find. Djurdjevka seems to be one of those dances that is more popular outside the country – among recreational dancers.