question

I wrote a code for getting number of months.The code is below can you check

                    
DECLARE @startDate DATETIME,                    
         @endDate  DATETIME;                    
SET @startDate='2007.03.16';                    
SET @endDate='2009.03.28';                    
DECLARE @wholepart  FLOAT;                    
DECLARE @fraction FLOAT;                    
  IF(MONTH(@startDate)=MONTH(@endDate))                     
  BEGIN                     
     IF (MONTH(@endDate)IN(1,3,5,7,8,10,12))                    
     BEGIN                     
      SELECT  @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
               @fraction  =DATEDIFF(DAY,@startDate,DATEADD(DAY,1,@endDate)) *1.0/31.0                    
            SELECT ROUND(@wholepart+@fraction,0) AS '31DAYS'                    
     END                    
     IF(MONTH(@endDate)IN(4,6,9,11))                     
      IF (DAY(@startDate)=16)                    
       BEGIN                     
        SELECT   @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
                 @fraction  =DATEDIFF(DAY,@startDate,DATEADD(DAY,1,@endDate)) *1.0/30.0                    
        SELECT ROUND(@wholepart+@fraction,0) AS '30DAYS'                    
     END                    
     ELSE                    
     BEGIN                    
          SELECT   @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
                   @fraction =DATEDIFF(DAY,DATEADD(MONTH,@wholepart,@startDate),@endDate) *1.0/30.0                    
         SELECT ROUND(@wholepart+@fraction,0) AS '30DAYS'                    
     END                    
     IF(MONTH(@startDate)=2)                     
       IF (DAY(@startDate)=15)                    
     BEGIN                    
         IF(YEAR(@startDate)%4=0)                    
         SELECT   @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
                 @fraction = DATEDIFF(DAY,DATEADD(MONTH,@wholepart,@startDate),DATEADD(DAY,1,@endDate)) *1.0/29.0                    
         ELSE                    
         SELECT   @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
                 @fraction = DATEDIFF(DAY,DATEADD(MONTH,@wholepart,@startDate),DATEADD(DAY,1,@endDate)) *1.0/28.0                    
          SELECT ROUND(@wholepart+@fraction,0) AS '28DAYS'                    
      END                     
      ELSE                    
      BEGIN                    
           SELECT   @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
             @fraction =DATEDIFF(DAY,DATEADD(MONTH,@wholepart,@startDate),@endDate) *1.0/28.0                    
           SELECT ROUND(@wholepart+@fraction,0) AS '28DAYS'                    
       END                    
 END                        
                    
IF(MONTH(@startDate)!=MONTH(@endDate))                    
BEGIN                    
   SELECT   @wholepart =DATEDIFF(MONTH,@startDate,@endDate) *1.0,                    
             @fraction =DATEDIFF(DAY,DATEADD(MONTH,@wholepart,@startDate),@endDate) *1.0/                    
                            CASE WHEN MONTH(@endDate) IN (1,3,5,7,8,10,12) THEN 31.0                     
                                 WHEN MONTH(@endDate) IN (4,6,9,11) THEN 30.0                    
                                 WHEN MONTH(@endDate)=2  AND (YEAR(@endDate)%4 = 0) THEN 29.0                    
                                 ELSE 28.0 END                    
                    
   SELECT ROUND(@wholepart+@fraction,0) AS 'NORMAL'                    
END                    

i am getting no of months as 48 can you fix this and send me why it coming