Date Picker Validation

What is the best way to get the data-error text to be correctly shown below the datepicker input? I get the red line when no selection is made, but i cannot get the error text to be shown. Also after it gets the invalid class added during validation, and then i select a date the red line still appears.  I tried using the built in onSet function to remove the invalid class but it didn't appear to work. <div class="md-form"> <input type="text" id="pickupStartDate" placeholder="Select a date" class="form-control datepicker validate dateselector" > <label for="pickupStartDate" data-error="Cannot be blank" data-success="" class="active">Pickup Start Date</label> </div>

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