function checkCalendar() {
  if (!$("#year").val().isInteger() || $("#year").val() < 1900 || $("#year").val() > 2100) {
    alert("Please enter a valid year.");
    return false;
  }
  
  return true;
}

function checkTracking() {
  if ($("#trackingnumber").val().trim().length == 0) {
    alert("Please enter your tracking number.");
    return false;
  }
  
  return true;
}

$(document).bind('ready',function() {
  $("#calendar").bind('submit',checkCalendar);
  $("#tracking").bind('submit',checkTracking);
});