input.ui-datepicker-trigger {
    color: #333;
    background-color: transparent;
    border: none;
    box-sizing: border-box;
    vertical-align: middle;
    margin-top: 1px;
    margin-bottom: 1px;
    height: 16px;
    line-height: 24px;
    padding: 0 3px;
    width: 22px;
}