The column header height can be adjusted using HeaderHeight property.
By default, column header height auto-fit is enabled. You need to turn it off when customizing the header height.
ASP.NET WebForms
<DayPilot:DayPilotCalendar ... HeaderHeight="30" ColumnHeaderHeightAutoFit="false" />
ASP.NET MVC
@Html.DayPilotCalendar("dpc", new DayPilotCalendarConfig { // ... HeaderHeightAutoFit = false, HeaderHeight = 30, // ... })
JavaScript
<div id="dp"></div> <script type="text/javascript"> var dp = new DayPilot.Calendar("dp"); dp.headerHeightAutoFit = false; dp.headerHeight = 30; // ... dp.init(); </script>