пардон, код забыл вложить
<style>
#container
{
margin-top: 60px;
position: absolute;
width: 2000px;
}
.day
{
position: relative;
display: inline;
}
.day h2
{
padding: 0 5px;
position: absolute;
left: 4px;
top: -65px;
}
.event
{
width: 50px;
height: 50px;
border: 1px solid black;
margin: 0 4px;
display: inline-block;
}
</style>
<script>
window.addEventListener('load', function(){
var container = document.getElementById('container');
var compStyle = window.getComputedStyle(container.getElementsByClassName('day')[1], null);
alert('width: ' + compStyle.width)
}, false)
</script>
<div id="container">
<div class="day">
<h2>День 1</h2>
<div data-event-id="0" class="event">1</div>
<div data-event-id="1" class="event">2</div>
<div data-event-id="2" class="event">3</div>
<div data-event-id="3" class="event">4</div>
</div>
<div class="day">
<h2>День 2</h2>
<div data-event-id="4" class="event">1</div>
<div data-event-id="5" class="event">2</div>
</div>
</div>
