Since the placeholder attribute is not supported yet, we can use the :before pseudo element of the input. However, we only want to show the placeholder if the input is empty and not focused. We can control the empty/not empty via a simple binding that checks the date data property as shown below.
Most of the magic happens in CSS though:
That’s about it. You can see a working demo in https://jsfiddle.net/cfbpso5v/3