diff --git a/projjpn/src/main/java/de/hs_fulda/ciip/projjpn/Birthdate.java b/projjpn/src/main/java/de/hs_fulda/ciip/projjpn/Birthdate.java
index 32ed901..9ab68bf 100644
--- a/projjpn/src/main/java/de/hs_fulda/ciip/projjpn/Birthdate.java
+++ b/projjpn/src/main/java/de/hs_fulda/ciip/projjpn/Birthdate.java
@@ -42,6 +42,14 @@ public class Birthdate {
 		year = y;
 	}
 	
+	/**
+	 * 
+	 * @param DD
+	 * @param MM
+	 * @param YYYY
+	 * @return true if date is valid.
+	 * @return false if date is invalid.
+	 */
 	public boolean isValid(int DD, int MM, int YYYY) {
 		if (DD < 1 || DD > 31) {
 			return false;