It is possible to use Width="100%". This will set the control width automatically to fill all the horizontal space (subject to the CSS width rules).

In the Calendar (http://www.daypilot.org/calendar.html) and the Month (http://www.daypilot.org/month.html) controls the cell width is set automatically to fill the control width (you only specify the number of columns, but not the width of individual columns).

In the Scheduler (http://www.daypilot.org/scheduler.html) it is necessary to set the column width manually (CellWidth property). The control width is set separately - if the cells don't fit there, a scrollbar will be displayed. It's not possible to set the cell width to auto at this moment.