diff --git a/du3/program.c b/du3/program.c
index c0c14a3..19fec70 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -24,6 +24,10 @@ if(m==2){
     return 0;    
     }    
 }
+if(m>12){
+    printf("Nespravny datum\n");
+    return 0;  
+}
 day+=7;
 if(m%2!=0 && day>31){
     day-=31;