You can start from the example given here,

http://help.infragistics.com/Help/NetAdvantage/ASPNET/2009.2/CLR3.5/html/WebSchedule_Add_a_Recurring_Appointment_Server_Side.html

in which you create an Appointment and a Recurrence programmatically, and then just create an AppointmentVariance for day 2 that has the different hours.  In the following example, I create a recurring activity called "Training," and on 12/21 it will be 9:00-17:00 local time; on 12/22 it will be 9:00-15:00 local time.

In my Page_Load (just in case you shake your head at why it didn't work the first time ;) ),

// Call DataBind() BEFORE adding objects programmatically
// to WebScheduleInfo, otherwise a call to DataBind() may
// Clear any contents that are already in the Activities Collection.
this.WebScheduleInfo1.DataBind();

// Example code for generating an in-memory Appointment,
// Recurrence and Variance.
this.CreateExampleVariance();

In the method, CreateExampleVariance,

// Create an Appointment (this is the Root Activity)
Appointment appt = new Appointment( this.WebScheduleInfo1);
appt.Subject = "Training";
appt.StartDateTime = new SmartDate( 2009, 12, 21, 9, 0, 0);
appt.Duration = new TimeSpan( 8, 0, 0);
appt.Key = "100";
appt.ResourceKey =
     this.WebScheduleInfo1.VisibleResources.UnassignedResource.Key;

// Create a Daily Recurrence (for 2 occurrences of the
// above Root Activity)
appt.CreateRecurrence();
appt.Recurrence.Period = RecurrencePeriod.Daily;
appt.Recurrence.PeriodMultiple = 1;
appt.Recurrence.MaxOccurrences = 2;

// Create a Variance that will override the 2nd occurence
// of the above Recurrence)
Activity variance = appt.CreateVariance(
     appt.StartDateTimeUtc.AddDays( 1.0),
     appt.StartDateTimeUtc.AddDays( 1.0));

// Since you are NOT changing the starting time, both args
// passed to CreateVariance are identical.

// Set a different duration on the Variance for Day 2, in
// this case Training runs from 9:00 to 15:00 local time
// instead of 9:00 to 17:00 as it did for Day 1.
variance.Duration = new TimeSpan( 6, 0, 0);

// Add the Root Activity to the WebScheduleInfo
// so that it shows up.
this.WebScheduleInfo1.Activities.Add( appt);

// NOTE: If you want the Appointment Variance to persist,
// you must add it to the Data Provider. You MAY need
// the following step (depending on your DP impl) before
// adding it to the Data Provider.
if (appt.VarianceKey == Guid.Empty)
{
     // You would only set this if this was the first variance
     // attached to the Root Activity's Recurrence.
     appt.VarianceKey = variance.VarianceKey = Guid.NewGuid();
}