Creating a Singleton class with builder capabilities

Consider the following hypothetical Singleton class DateSingleton which currently looks like the following:

public class DateSingleton {

  private static DateSingleton instance = new DateSingleton();

  private String year;
  private String month;
  private String day;

  private DateSingleton() {
  }

  public static DateSingleton getInstance(){
    return instance;
  }
}

This Singleton can be thought of as a date keeper, and only one of them will exist for my entire web application. I would like to be able to make the following type of builder-style call to assign my state:

DateSingleton.getInstance().year("2015").month("February").day("25");

Can someone suggest what code I would need to add to the DateSingleton class in order to make this possible? Is it considered bad practice to make a Singleton a builder?

I realize that I could just add getters and setters to accomplish the same funtionality. But I want to move away from this, as there may be many properties in this Singleton and the builder pattern makes the code much easier to use and read.