Make previous calendar dates not selectable in ASP.NET
In order to make all dates before the current date, not able to be selected, in the onDayRender event for your Calendar: if (e.Day.Date < DateTime.Today) { e.Day.IsSelectable = false; } To make it more obvious to the end user, also add: e.Cell.BackColor = Drawing.Color.GhostWhite; e.Cell.ForeColor = Drawing.Color.Gainsboro;