apply timezone on displayed time

code/src/main.c

@@ -57,6 +57,15 @@ int main(void){
             cli();
             DS3231_read(clock);
             sei();
+
+            // convert from bcd and back
+            int8_t hour = (10 * (clock[2] & 0xF0)>>4) + (clock[2] & 0x0F);
+            hour += menu_val_timezone;
+            hour %= 24;
+            if(hour < 0)
+                hour = 24 + hour;
+            clock[2] = ((hour/10)<<4)|(hour % 10);
+
             clock_to_buffer(clock);
 
             PORTC = (PORTC & (~DOT)) | (clock[0]%2) << 4; // blink dots