Google App Script - Time Stamp for Google Sheets

gistfile1.txt

// this will check a range, and if cell is in range, then 
//add a time stamp to the top of the column wherein the change was made.

function onEdit(e) 
{
  var editRange = { // B4:J6
    top : 9,
    bottom : 255,
    left : 2,
    right : 7
  };

  // Exit if we're out of range
  var thisRow = e.range.getRow();
  if (thisRow < editRange.top || thisRow > editRange.bottom) return;

  var thisCol = e.range.getColumn();
  if (thisCol < editRange.left || thisCol > editRange.right) return;

  // We're in range; timestamp the edit
  var ss = e.range.getSheet();
  ss.getRange(7,thisCol)   // row 7, in which ever column is edited.
    .setValue(new Date()); // Set time of edit in row 7, relevant column
}