import java.util.*;
import java.text.*;
public class cpromG {
public static void main(String [] args) {
Scanner scn = new Scanner(System.in);
String ls = System.getProperty("line.separator");
scn.useDelimiter(ls);
int n = scn.nextInt();
for(int x=0;x<n;x++) {
String s = scn.next();
StringTokenizer st = new StringTokenizer(s, " ");
StringTokenizer startTime = new StringTokenizer(st.nextToken(),":");
StringTokenizer endTime = new StringTokenizer(st.nextToken(),":");
int startHour = Integer.parseInt(startTime.nextToken());
int startMinute = Integer.parseInt(startTime.nextToken());
int endHour = Integer.parseInt(endTime.nextToken());
int endMinute = Integer.parseInt(endTime.nextToken());
DecimalFormat df = new DecimalFormat("00");
if(startHour > endHour) {
int hour = 12 - startHour + endHour;
int minute = 0;
if(startMinute < endMinute ) {
minute = endMinute - startMinute;
}
else {
minute = 60 - startMinute + endMinute;
hour = hour-1;
}
if(hour >= 8)
minute = 0;
System.out.println(df.format(hour) +":" +df.format(minute));
}
else {
int hour = endHour - startHour;
int minute = 0;
if(startMinute < endMinute ) {
minute = endMinute - startMinute;
}
else {
minute = 60 - startMinute + endMinute;
hour = hour-1;
}
if(hour >= 8)
minute = 0;
System.out.println(df.format(hour) +":" +df.format(minute));
}
}
}
}