diff -r 231a79d93c0c -r 685af47592b5 src/chess/rules.c
--- a/src/chess/rules.c	Thu Apr 16 19:29:11 2026 +0200
+++ b/src/chess/rules.c	Thu Apr 16 19:49:16 2026 +0200
@@ -36,6 +36,7 @@
 #include "king.h"
 
 #include <string.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <sys/time.h>
 
@@ -816,3 +817,14 @@
 
     return used_time >= total_time ? 0 : total_time - used_time;
 }
+
+void print_clk(uint16_t time, char *str, bool always_hours) {
+    unsigned hours = time / 3600;
+    unsigned minutes = (time % 3600) / 60;
+    unsigned seconds = time % 60;
+    if (hours > 0 || always_hours) {
+        snprintf(str, 9, "%02u:%02u:%02u", hours, minutes, seconds);
+    } else {
+        snprintf(str, 6, "%02u:%02u", minutes, seconds);
+    }
+}