function SubtractDateFromDateAsDayTime(FirstValue: TDateTime;
      SecondValue: TDateTime; DayTimeIntervalType:
      TEDBDayTimeIntervalType): TEDBDayTimeInterval

 In ElevateDB, day-time intervals are Int64 values that represent the number of milliseconds that have elapsed between two points in time. Use the TEDBEngine DayTimeIntervalToSQLStr method to convert a day-time interval into a readable string.