$(document).ready(function() {

  $form = $('#calendar_form');
  target = $form.attr('action');

  $form.submit(function () {
    var from = $('input#date_from').val();
    var to = $('input#date_to').val();
    var pattern = /^[0-9]{4}-[0-9]{2}-[0-9]{2}$/;
    var out = '';

    if (pattern.test(from)) {
      out = 'from='+from;
    }
    if (pattern.test(to)) {
      if (out=='') {
        out = 'to='+to;
      } else {
        out += "&to="+to;
      }
    }
    if (out!='') {
      if (target=='/browse') {
        target += '?'+out;
      } else {
        target += '&'+out;
      }
      window.location = target;
    }
    return false;
  }); // form.submit
}); // $(document).ready(function()