What is the correct way to resize datetime input field for bootstrap-datetimepicker?

Question

css

Hello.
I decided to transfer the dashboard with a date and time range selection to bootstrap-datetimepicker.
https://github.com/Eonasdan/bootstrap-datetimepicker

$(function () {              
                $("#datetime_input").datetimepicker({
                    locale: 'ru'
                });
                $("#datetime_output").datetimepicker({
                    locale: 'ru'
                });
   });

<div class="row">
        <span>C</span>
        <div class='col-xs-3'>
            <div class="form-group">
                <div class='input-group date' id='datetime_input'>
                    <input id="INPUT_DATETIME" type='text' class="form-control" value="${INPUT_DATETIME}"/>
                    <span class="input-group-addon">
                        <span class="glyphicon glyphicon-calendar"></span>
                    </span>
                </div>
            </div>
        </div>

        <span>По</span>
        <div class='col-sm-3'>
            <div class="form-group">
                <div class='input-group date' id='datetime_output'>
                    <input id="OUTPUT_DATETIME" type='text' class="form-control" value="${OUTPUT_DATETIME}"/>
                    <span class="input-group-addon">
                        <span class="glyphicon glyphicon-calendar"></span>
                    </span>
                </div>
            </div>
        </div>
</div>

The question arose how to change the size of the date and time input field.
To begin with, I'm interested in how to reduce the size of the input field.
ps
On the Internet, the question seems to have been similar already
stackoverflow.com/questions/34941412/how-to-resize... ,
stackoverflow.com/questions/19404620/reduce-size-a...
BUT the proposed solutions did not work.