Width accepts an empty value (and it's the default value). This behavior corresponds to display:block style.

You can use any value acceptable for width CSS style.

JavaScript Example

<div id="dpc"></div>
<script type="text/javascript">
  var dpc = new DayPilot.Calendar("dpc");
  dpc.width = "100%";
  // ...
  dpc.init();
</script>

ASP.NET WebForms Example

<DayPilot:DayPilotCalendar 
  runat="server" 
  id="DayPilotCalendar1"
  Width="100%" ...
/>

ASP.NET MVC Example

@Html.DayPilotCalendar("dpc", new DayPilotCalendarConfig {
  BackendUrl = ResolveUrl("~/Calendar/Backend"),
  Width = "100%",
  ...
})

Java Example (JSP)

<div id="dpc"></div>
<script type="text/javascript">
  var dpc = new DayPilot.Calendar("dpc");
  dpc.backendUrl = "${pageContext.request.contextPath}/dpc";
  dpc.width = "100%";
  // ...
  dpc.init();
</script>