Pick Date From a Calendar in Selenium

public static void main(String[] args) throws InterruptedException {

WebDriver driver = new FirefoxDriver();
driver.get("http://jqueryui.com/datepicker/");
driver.manage().window().maximize();
driver.switchTo().frame(0);
driver.manage().timeouts().implicitlyWait(3000, TimeUnit.MILLISECONDS);
driver.findElement(By.xpath("//*[@id='datepicker']")).click();
driver.manage().timeouts().implicitlyWait(3000, TimeUnit.MILLISECONDS);
driver.findElement(By.xpath("//*[@id='ui-datepicker-div']/div/a[2]/span")).click();
List column = driver.findElements(By.tagName("td"));
for (WebElement j : column)
{
if (j.getText().contains("13")){
j.findElement(By.linkText("13")).click();
break;
}
}
Thread.sleep(5000);
}