CREATE FUNCTION "IsLastYear" (
IN "ADate" DATE)
RETURNS BOOLEAN
BEGIN
 DECLARE Result BOOLEAN DEFAULT False;
 DECLARE EndDate, StartDate DATE;
 DECLARE iYear INTEGER;

 SET EndDate = CURRENT_DATE;
 SET iYear = EXTRACT(YEAR, EndDate)-1;
 SET StartDate = CAST(CAST(iYear AS VARCHAR) + '-01-01' AS DATE);
 SET EndDate = CAST(CAST(iYear AS VARCHAR) + '-12-31' AS DATE);

 IF ADate BETWEEN StartDate AND EndDate THEN
   SET Result = True;
 ELSE
   SET Result = False;
 END IF;

 RETURN Result;
END

DESCRIPTION 'Boolean function to return TRUE if the given date belongs to last year.'

There are some nice shortcuts in EDB. Consider this alternative.

CREATE FUNCTION "IsLastYear" (IN "ADate" DATE)
RETURNS BOOLEAN
BEGIN
 RETURN (EXTRACT(YEAR FROM ADate) = EXTRACT(YEAR FROM CURRENT_DATE) - 1);
END