time = '10:00';
shift = {{'NY','+5:00'}};
numClocks = length(shift);

for ndx = 1:numClocks
    
    [atlhr, minutes] = strtok(time, ':');
    atlhr = str2num(atlhr);
    [hr, ~] = strtok(shift{ndx}{2}, ':');
    hrshift = hr(1);
    hr = str2num(hr(2:end));
    
    if hrshift == '+'
        hr = atlhr + hr;
    else
        hr = atlhr - hr;
    end
    
    if hr >= 12
        hr = mod(hr, 12);
    end
   
   fprintf("%d%s\n",hr,minutes);
end