It means St. George's Day or Djurdjevdan, in gypsy language. I found that out watching the musical on Swedish tv and there were subtitles of course. So glad i found that out. :)
My theory on Feds is that they're like mushrooms: feed them *beep* keep them in the dark.
It only coincides with Orthodox St. George's Day. It's originally a Turkish spring holiday Hederlez, meaning (Prophet) Khidr and Elijah's Day, taken by the Gypsies in the form Ederlezi.
Roma people converted to islam when they settled in the Ottoman Empire, and adopted many of Turkish customs. When the Balkans were reclaimed by Orthodox countries, they massively converted to Orthodox Christianity. Since Ederlezi coincided with Orthodox St. George's Day, which is also a spring festival, it was tolerated that Gypsies celebrate it, as it was thought to be their way of celebrating St. George's Day.