解决方法
这有效：
.date-popup {
opacity: 0;
width: 0;
}
<p class="input-group">
<span class="input-group-btn">
<input type="text" class="date-popup"
datepicker-popup="{{format}}" ng-model="dt"
is-open="opened" datepicker-options="dateOptions"
date-disabled="disabled(date,mode)" ng-required="true"
show-weeks="false" close-text="Close">
<button type="button" class="btn btn-default" ng-click="open($event)">
<i class="glyphicon glyphicon-calendar"></i>
</button>
</span>
</p>
