A google apps script for google doc to a) create a new menu to insert the current date b) insert the date

insert_date_apps_script.js

/**
 * The onOpen function runs automatically when the Google Docs document is
 * opened. Use it to add custom menus to Google Docs that allow the user to run
 * custom scripts. For more information, please consult the following two
 * resources.
 *
 * Extending Google Docs developer guide:
 *     https://developers.google.com/apps-script/guides/docs
 *
 * Document service reference documentation:
 *     https://developers.google.com/apps-script/reference/document/
 */
function onOpen() {
  // Add a menu with some items, some separators, and a sub-menu.
  DocumentApp.getUi().createMenu('Custom Utils')
      .addItem('Insert Date', 'insertAtCursor')
      .addToUi();
}

/**
 * Inserts the date at the current cursor location in boldface.
 */
function insertAtCursor() {
  var doc = DocumentApp.getActiveDocument()
  var cursor = doc.getCursor();

  if (cursor) {
    // Insert current date, bolded, at cursor position. Move cursor to end of date.
    // Insert newline, disable bold, move cursor one line down.
    var date = formatDate(new Date)
    var date_element = cursor.insertText(date);
    if (date_element) {
      date_element.setBold(true);
      var end_of_date_str_pos = doc.newPosition(date_element, date.length)
      if (end_of_date_str_pos) {
        doc.setCursor(end_of_date_str_pos)
        var newline_element = cursor.insertText("\n");
        if (newline_element) {
          newline_element.setBold(false);
          var newline_pos = doc.newPosition(newline_element, 1)
          if (newline_pos) {
            doc.setCursor(newline_pos)
          } else {
            DocumentApp.getUi().alert('Cannot move cursor to this position ' + newline_pos + '.');
          }
        } else {
          DocumentApp.getUi().alert('Cannot insert text at this cursor location.');
        }        
      } else {
        DocumentApp.getUi().alert('Cannot move cursor to this position ' + end_of_date_str_pos + '.');
      }
    } else {
      DocumentApp.getUi().alert('Cannot insert text at this cursor location.');
    }
  } else {
    DocumentApp.getUi().alert('Cannot find a cursor in the document.');
  }
}

function formatDate(date) {
    var d = new Date(date),
        month = '' + (d.getMonth() + 1),
        day = '' + d.getDate(),
        year = d.getFullYear();

    if (month.length < 2) 
        month = '0' + month;
    if (day.length < 2) 
        day = '0' + day;

    return [year, month, day].join('.');
}