| Country | Day | Month | Names |
 Austria | 21 | May | Christoph, Constantin, Josef, Julio |
 Bulgaria | 21 | May | Elena, Konstantin, Kosta, Kostadin, Kostadinka, Lenko, Dicho, Lenko, Dinko, Elenko, Eli, Elin, Elka, Ilona, Kojcho, Kostadina, Kostadinko, Kuncho, Stamen, Stanimir, Stanimira, Stanka, Stoil, Stoyan, Stoian, Stoyanka, Trayko, Dinko |
 Croatia | 21 | May | Eugen, Serapion |
 Czechia | 21 | May | Monika |
 Denmark | 21 | May | Helene |
 Estonia | 21 | May | Konstantin, Kostel, Tiino, Kindel |
 Finland | 21 | May | Konsta, Kosti, Konstantin |
 France | 21 | May | Constantin |
 Greece | 21 | May | Konstantinos, Kostas, Tina, Dina, Eleni, Helen |
 Hungary | 21 | May | Konstantin |
 Italy | 21 | May | Vittorio |
 Latvia | 21 | May | Ernestine, Ingmars, Vinija |
 Lithuania | 21 | May | Vaidivutis, Valentas, Vydmina |
 Norway | 21 | May | Eli, Ellen, Helene |
 Poland | 21 | May | Donat, Donata, Jan, Kryspin, Przecława, Pudens, Tymoteusz, Walenty, Wiktor, Wiktoriusz |
 Slovakia | 21 | May | Zita |
 Spain | 21 | May | Constantino, Virginia, Giselle, Valente |
 Sweden | 21 | May | Conny, Konstantin |
 Ukraine | 21 | May | Constantine, Constance, Helen |
 USA | 21 | May | Adelric, Adiel, Audric, Keaton, Kendrick |
