Conference noted::hackers_v1

    Sorry, I don't have examples on the E-net to pull.  But it is trivial,
    use the LIB$ADDX and LIB$SUBX routines to do your arithmetic.  Then,
    all you have to remember is that VMS uses the sign bit to determine
    if it is a delta time or an absolute time.  So get your delta times
    negative.
    
    FJBlando
    (Who has done it many times)

There is an bunch of code around for this.  I thought I saw it posted in
this file a while back.  If I get a chance, I'll look for it.

	PROGRAM FUTURE
C ------------------------------------------------------------------------
C 	  This program calculates a future date from a given date.  The
C	  user specifies a base date and how many days future to go.
C	  The program calculates this future date and reports what it
C	  will be.
C
C 	  AUTHOR:  Barry D. Dysert
C ------------------------------------------------------------------------

	IMPLICIT INTEGER*4 (A-Z)

	INTEGER*4 timadr_q(2), future_q(2), addend_q(2), offset_q(2)
	INTEGER*4 srcdsc_l2, dstdsc_l2

	INTEGER*2 srcdsc_w1, dstdsc_w1

	BYTE srcdsc(8), dstdsc(8)

	CHARACTER ndays_t*12, offset_t*12, prod_t*63, timbuf_t*23

	LOGICAL*1 tenflag

	EQUIVALENCE (srcdsc_w1, srcdsc(1)), (srcdsc_b3, srcdsc(3))
	EQUIVALENCE (srcdsc_b4, srcdsc(4)), (srcdsc_l2, srcdsc(5))
	EQUIVALENCE (dstdsc_w1, dstdsc(1)), (dstdsc_b3, dstdsc(3))
	EQUIVALENCE (dstdsc_b4, dstdsc(4)), (dstdsc_l2, dstdsc(5))

	EXTERNAL DSC$K_DTYPE_Q, DSC$K_DTYPE_T, DSC$K_CLASS_S

C ------------------------------------------------------------------------

	offset_t='864000016384'	! there are 864000016384 units in 1 day
	offset_q(1)=711573504
	offset_q(2)=201

C -----	  get base date

10	TYPE 400
400	FORMAT(/'$Enter date (dd-mmm-yyyy): ')
	READ(*,401,END=99) timbuf_t
401	FORMAT(a)

C	  convert it to system time

	status=STR$UPCASE(timbuf_t,timbuf_t)
	IF (.not. status) CALL LIB$STOP(%val(status))

	length=INDEX(timbuf_t,' ')-1
	IF (length .le. 0) length=LEN(timbuf_t)

	status=SYS$BINTIM(timbuf_t(1:length),timadr_q)
	IF (.not. status) CALL LIB$STOP(%val(status))

C -----	  get number of days future

	TYPE 402
402	FORMAT('$How many days future?     ')
	READ(*,*,END=99) ndays

C -----
C -----	  future_q date will be calculated as:
C
C	  Q_fut_date = Q_given_date + ndays*864000016384
C
C	  the kicker is that in order to use STR$MUL, ndays must be
C	  converted to a decimal string (via OTS$CVT_L_TI); then
C	  convert the product to a quadword (via LIB$CVT_DX_DX); then
C	  add this quadword to the given_date (via LIB$ADDX).
C -----
C -----	  if ndays is a multiple of 5, CVT_L_TI won't tack the extra
C -----	  zeros on the end; instead it will set prodexp; it would then be
C -----	  a pain to tack the zeros on ourselves, so to get around it, just
C -----	  make sure ndays isn't a multiple of 5.  We'll add 1 to it if it
C -----	  is, and then subtract the offset after everything's done, just
C -----	  before the ASCTIM.

	tenflag=.FALSE.
	IF (MOD(ndays,5) .eq. 0) THEN
	   ndays=ndays+1
	   tenflag=.TRUE.
	ENDIF

C -----	  convert ndays to string

	status=OTS$CVT_L_TI(ndays,ndays_t,%val(12))
	IF (.not. status) CALL LIB$STOP(%val(status))

C -----	  multiply ndays by offset

	status=STR$MUL(0,0,ndays_t,0,0,offset_t,prodsign,prodexp,prod_t)
	IF (.not. status) CALL LIB$STOP(%val(status))

C -----	  convert the result string to a quadword

	srcdsc_w1=63				! length
	srcdsc_b3=%LOC(DSC$K_DTYPE_T)		! data type T
	srcdsc_b4=%LOC(DSC$K_CLASS_S)		! class S
	srcdsc_l2=%LOC(prod_t)			! address to be converted

	dstdsc_w1=8				! length
	dstdsc_b3=%LOC(DSC$K_DTYPE_Q)		! data type Q
	dstdsc_b4=%LOC(DSC$K_CLASS_S)		! class S
	dstdsc_l2=%LOC(addend_q)		! address of destination

	status=LIB$CVT_DX_DX(srcdsc,dstdsc)
	IF (.not. status) CALL LIB$STOP(%val(status))

C -----	  now add the addend_q to the given date to produce future_q date

	status=LIB$ADDX(addend_q,timadr_q,future_q)
	IF (.not. status) CALL LIB$STOP(%val(status))

C -----	  if ndays was a multiple of 5, we added an extra day so now we
C -----	  must subtract off the offset to get back to what we should have

	IF (tenflag) THEN
	   status=LIB$SUBX(future_q,offset_q,future_q)
	   IF (.not. status) CALL LIB$STOP(%val(status))
	ENDIF

C -----
C -----	  convert system time of future_q date back to ascii for output
C -----

	status=SYS$ASCTIM(,timbuf_t,future_q,%val(0))
	IF (.not. status) CALL LIB$STOP(%val(status))
	TYPE 403, timbuf_t(1:11)
403	FORMAT(' future date is ',a)
	GO TO 10

C -----	  bye bye

99	CALL EXIT
	END

    Or you can use V5. There are LIB$SUB_TIMES and other neato
    runtime library routines for dealing with times.
    
    Kevin

    Also, instead of messing with trying to change the sign, you can
    use LIB$DAY, LIB$EMUL and SYS$FAO (in that order) to convert the
    final delta time into something printable.  Look at the source for
    the accounting utility for more info (or I can post a plagiarized
    version in PASCAL).
    
    -r