Defaulting a SPFieldLink like All Day Event in Calender

Use a Console Applicationa and run this.

// Don’t forget this
using System.Reflection;
...
using(SPSite site =
new SPSite("http://yoursite"))
{
using(SPWeb web = site.OpenWeb())
{
SPList list = web.Lists["Calendar"];
SPContentType ct = list.ContentTypes["Event"];
SPFieldLink fieldLink = ct.FieldLinks["All Day Event"];
// Now comes the magic
Type type = typeof(SPFieldLink);
PropertyInfo pi = type.GetProperty("Default", BindingFlags.NonPublic | BindingFlags.Instance);
pi.SetValue(fieldLink, "1", null);
ct.Update();
}
}