JavaScript Code

document.getElementById('signatureField1').addEventListener('input', function() {
  if (this.value) {  // checks if the input field has a value
    var timestamp1 = new Date().toISOString();
    document.getElementById('timestampField1').value = timestamp1;
  }
});

document.getElementById('signatureField2').addEventListener('input', function() {
  if (this.value) {  // checks if the input field has a value
    var timestamp2 = new Date().toISOString();
    document.getElementById('timestampField2').value = timestamp2;
  }
});