HTML

add placeholder in input type date

<input type="text" placeholder="Date of birth" onfocus="(this.type='date')"> 

html date placeholder

<input placeholder="Date" class="textbox-n" type="text" onfocus="(this.type='date')" id="date">

display placeholder in date input

<input type="text" name="lead_departure_date" class="form-control" placeholder="Departure Date" id="lead_departure_date" onfocus="(this.type='date')" onblur="(this.type='text')" required>