Select a date from Jquery, date picker using selenium webdriver - selenium

Question

Go to the Official Website of Jquery https://jqueryui.com/datepicker/
It's not allow be to click on input text even it's have unique id="datepicker" getting an error element not found Exception but when i runs locally by adding jquery date picker it works likes a charm. can somebody help me can't able to figure it out!
2) By using this url i can select anything but it not works with jquery official site as i mentioned above https://jqueryui.com/resources/demos/datepicker/default.html
Below is my actual code that is not getting work
System.setProperty("webdriver.chrome.driver","C:\\ProgramFiles\\chromedriver.exe");
driver=new ChromeDriver();
driver.manage().window().maximize();
driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);
driver.get("https://jqueryui.com/datepicker/");
Thread.sleep(5000);
driver.findElement(By.id("datepicker")).click();

Answer 1

The element with id="datepicker" is within a frame. So we have to switch to the intended frame first, then locate the element and then call the click() method as follows:
System.setProperty("webdriver.chrome.driver", "C:\\Utility\\BrowserDrivers\\chromedriver.exe");
WebDriver driver=new ChromeDriver();
driver.manage().window().maximize();
driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);
driver.get("https://jqueryui.com/datepicker/");
driver.switchTo().frame(driver.findElement(By.xpath("//iframe[#class='demo-frame'][#src='/resources/demos/datepicker/default.html']")));
driver.findElement(By.id("datepicker")).click();
System.out.println("Datepicker Clicked");