A Google Script for spreadsheets to covert a selection of cells to mins:secs

gistfile1.js

function sensible_time() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var data = sheet.getActiveRange().getValues();
  for (var i = 0; i < data.length; i++) {
    for (var j = 0; j < data[i].length; j++) {
     if (data[i][j]) {
       var range = sheet.getRange(24+i, j+1);
       time = data[i][j];
       var mins = ~~(time / 60);
       var secs = time % 60;
       Logger.log(mins+":"+secs+"");
       range.setValue(mins+":"+secs);
     }
   }
  }
}