public Day(SerialDate serialDate){
  ParamChecks.nullNotPermitted(serialDate,"serialDate");
  this.serialDate=serialDate;
  peg(Calendar.getInstance());
}

public Day ( SerialDate serialDate ) { ParamChecks . nullNotPermitted ( serialDate , "serialDate" ) ; this . serialDate = serialDate ; peg ( Calendar . getInstance ( ) ) ; }
constructs a new one day time period .
