Field <input> superimposing calendar field

Question

Good morning!! I have the following problem, I have an icon text field, but when I select the calendar field below, the input field is overwriting the calendar field. Any idea what it might be?? Below is the code and the self-explanatory image.

<div class="form-group">
    <label>Nome</label>
    <div id="listas">
    <div class="input-group">
        <input class="form-control" name="colaborador" id="colaborador" value="" required>
        <span class="input-group-btn">
           <button class="btn btn-primary" type="button" id="add_field"><i class="fa fa-plus"></i></button>
        </span>
        </div>
    </div>
</div>                              
<div class="form-group">
    <label>Data Inicial</label>
    <input class="form-control" name="dataInicial" value="" id="datepicker" data-mask="00/00/0000" style="width:100px" required>
</div>

Answer 1

In class .ui-datapicker place:

.ui-datapicker {
  z-index 9999 !important;
}

That will solve your problem.