#include<iostream>
#include<cstring>
using namespace std;
int main(){
    int n;
    string s1,s2;
    cin>>n;
    cin.ignore(1024,'\n');
    for(int i=0;i<n;i++){
        getline(cin,s1);
        getline(cin,s2);
        int t1,t2;
        t1=stoi(s1.substr(15,2))+stoi(s1.substr(12,2))*60+
            stoi(s1.substr(9,2))*3600-stoi(s1.substr(6,2))-
            stoi(s1.substr(3,2))*60-stoi(s1.substr(0,2))*3600;
        t2=stoi(s2.substr(15,2))+stoi(s2.substr(12,2))*60+
            stoi(s2.substr(9,2))*3600-stoi(s2.substr(6,2))-
            stoi(s2.substr(3,2))*60-stoi(s2.substr(0,2))*3600;
        if(s1.size()>18)t1+=stoi(s1.substr(20,1))*3600*24;
        if(s2.size()>18)t2+=stoi(s2.substr(20,1))*3600*24;
        printf("%02d:%02d:%02d\n",(t1+t2)/2/3600,(t1+t2)/2%3600/60,(t1+t2)/2%60);
    }
    return 0;
}