IncWeek returns the given date, incremented by the number of weeks given as the ANumberOfWeeks parameter.
ANumberOfWeeks can be negative, to return a date, earlier by the specified number of weeks.
The time of day specified by AValue, is copied to the result.
Declaration: Function IncWeek(const AValue: TDateTime; const ANumberOfWeeks: Integer): TDateTime;
This is a simple example.