html - How to change opacity of date type placeholder text? -

registration page image

i using:

<span class="input input--isao"> <input class="input__field input__field--isao" type="date" id="dateofbirth" name="dateofbirth"/> <label class="input__label input__label--isao" for="dateofbirth" data-content="date of birth"> <span class="input__label-content input__label-content--isao">date of birth</span> </label> </span>  ::-webkit-input-placeholder {   opacity:  0.4; } 

how placeholder text date 0.4 opacity. placeholder yyyy-mm-dd automatic, not inputted me. pls see image.

you can use datable.js query plugin mask text input date input