function startAll() {
  startB();
  startE();
  startH();
  startK();
}

function startB(){
  startTime("B");
}
function startE(){
  startTime("E");
}
function startH(){
  startTime("H");
}
function startK(){
  startTime("K");
}

function startTime(column) {
  var timeNow = Utilities.formatDate(new Date(), "GMT+2:00", "''HH:mm:ss")
  var currentCell = findLastIndex(column);
  var nextCell = currentCell + 1;
  var sheet = SpreadsheetApp.getActiveSheet().getRange(column + nextCell).setValue(timeNow).setNumberFormat("HH:mm:ss");
}

function findLastIndex(column) {
  var lastRow = SpreadsheetApp.getActiveSheet().getMaxRows();
  var values = SpreadsheetApp.getActiveSheet().getRange(column + "1:" + column + lastRow).getValues();

  for (; values[lastRow - 1] == "" && lastRow > 0; lastRow--) {}
  return lastRow;
}

function clearAll() {
  SpreadsheetApp.getActiveSheet().getRange('B6:B26').setValue("");
  SpreadsheetApp.getActiveSheet().getRange('E6:E26').setValue("");
  SpreadsheetApp.getActiveSheet().getRange('H6:H26').setValue("");
  SpreadsheetApp.getActiveSheet().getRange('K6:K26').setValue("");

}