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

ASP.NET WebForms Example

<DayPilot:DayPilotMonth 
  runat="server" 
  id="DayPilotMonth1"
  Width="100%"
  ...
/>

ASP.NET MVC Example

@Html.DayPilotMonth("dps", new DayPilotMonthConfig {
  BackendUrl = ResolveUrl("~/Month/Backend"),
  Width = "100%",
  ...
})

Java Example (JSP)

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