Break down number of days in hospital by calendar month

*(Q) I would like to determine the number of bed-days used per month with 2 dates-intake & exit. I would like the calculation by month.
*	No intake end month1 month2 month3 etc...
*	1 1/5/01 2/5/01 25 5 0 
*	2 2/7/01 3/7/01 0 21 7 
*	3 4/3/01 5/25/01 ? ? ?

*(A) Posted to SPSSX-L by rlevesque@videotron.ca on 2001/11/20.

* Note: The following syntax is not completely general. 
*	It assumes that all dates are in the same calendar year.

DATA LIST LIST /id(F8) datein(ADATE) dateout(ADATE).
BEGIN DATA
1 1/5/01 2/5/01
2 2/7/01 3/7/01
3 4/3/01 5/25/01
4 2/1/01 4/4/01
5 1/31/01 4/1/01
6 7/1/01 9/29/01
7 9/10/01 12/30/01
END DATA.
LIST.

VECTOR month(12F8).
COMPUTE #oneday=24*60*60.
LOOP mth=1 TO 12.
COMPUTE beg1=MAX(datein , DATE.DMY(1,mth,XDATE.YEAR(datein))).
COMPUTE end1=MIN(dateout + #oneday, DATE.DMY(1,mth+1,XDATE.YEAR(datein))).
COMPUTE month(mth)=max(0, CTIME.DAYS(end1 - beg1)).
END LOOP.
EXECUTE.