This recipe requires a custom Apex class to encapsulate the Date primitive. To do so, perform the following steps:

Opening the following URL in your browser displays the ContactDateEdit page: https://<instance>/apex/ContactDateEdit?id=<contact_id>.

Here, <instance> is the Salesforce instance specific to your organization, for example, na6.salesforce.com, and <contact_id> is the ID of any contact in your Salesforce instance.

The Visualforce page controller declares a DateContainer property that will be used to capture the contact's date of birth.

public DateContainer dob {get; set;}
private Contact cont;
private ApexPages.StandardController stdCtrl {get; set;}
  
public ContactDateEditExt(ApexPages.StandardController std)
{
  stdCtrl=std;
  cont=(Contact) std.getRecord();
  dob=new DateContainer(cont.BirthDate);
}

The custom component that manages the Date of Birth section defines the following two attributes:

The component controller defines properties for each of the day, month, and year elements of the date. Each setter for these properties attempts to construct the date if all of the other elements are present. This is required as there is no guarantee of the order in which the setters will be called when the Save button is clicked and the postback takes place.

public Integer year {get; 
    set {
          year=value;
          updateContainer();
          }
    }
  
private void updateContainer()
{
  if ( (null!=year) && (null!=month) && (null!=day) )
  {
    Date theDate=Date.newInstance(year, month, day);
    dateContainer.value=theDate;
  }
}

When the contained date primitive is changed in the updateContainer method, this is reflected in the page controller property, which can then be used to update a field in the contact record.

public PageReference save()
{
  cont.BirthDate=dob.value;
  
  return stdCtrl.save();
}