GoogleApps Script: Label all old Gmails

gistfile1.txt

// Use at: https://script.google.com/

function findOldMails() {
  // Find UserLabel (Needs to exist)
  var label = GmailApp.getUserLabelByName("old");
  
  // Setting our query
  var query="older_than:1y -label:old";
  
  
  var numThreads=400;
  var lastStart=-1;
  while(numThreads>0) {
    var threads=GmailApp.search(query);    
    for(var i=0;i<threads.length;i++) {           
        threads[i].addLabel(label);       
    }
    numThreads=threads.length;
   
  }    
}