diff --git a/du3/program.c b/du3/program.c
index 19fec70..24c6f42 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -24,7 +24,7 @@ if(m==2){
     return 0;    
     }    
 }
-if(m>12){
+if(m>12 || y<0){
     printf("Nespravny datum\n");
     return 0;  
 }