On May 21st the Christian Church commemorates the two Saints Equal-to-the Apostles – the Emperor Constantine the Great and his mother Helen. In the year 313 Emperor Constantine proclaimed the Edict of Milan which introduced Christianity as one of the official religions in the vast Roman empire. In Bulgaria the cult to St. Constantine and St. Helen is highly popular in Strandzha Mountain where their feast day is called Kostadin’s Day. On it there is a very interesting ritual – fire dancing, called nestinarstvo. The day of St. Helen and St. Kostadin is believed to be hataliya, a bad day and that is why no work should be done so as not to infuriate the saint.

In the Rodope region Kostadinovden is a holiday respected by the shepherds and is called Predoy, Mandra, or Otbiv. On this day they milk the sheep and wean the lambs from their mothers. Common tables are arranged beside the houses. Kostadin’s Day is known as Karchana in the Thracian villages and it is known that on this day the sun burns heavily. That is why the livestock is kept in the barns so as not to “karchanyasa”, i.e. not to get a sunstroke.

On May 21st a name day celebrate all those bearing the names Konstantin, Kostadin, Kostadinka, Elena, Elenko.