Need help with Windows date and time.

[mark smit]

Hello all,

Can somebody explain to me how to ADD or SUBTRACT a single day from the SYSTEMTIME structure. I convert the SYSTEMTIME structure to a 64bit number with SystemTimeToFileTime and I tried adding what I thought was a day but nothing changed when I put my result back through FileTimeToSystemTime.

1000 miliseconds in a second
60 seconds in a minute
60 minutes in an hour
24 hours in a day

so...

1Day = (1000 * 60 * 60 * 24)


All I want is to add or subtract a day from the SYSTEMTIME structure and have the Month and Year adjust accordingly, could somebody help here I'm about ready to toss my computer out the fourth floor here!


Thanks



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Cheers!

[Fred Oxenby]

You should *NEVER* perform a math on a SYSTEMTIME structure.
That is rule no one what ever someone else tells you.
Use SystemTimeToFileTime to get a FILETIME struct
The FILETIME structure is a 64-bit value representing the number
of 100-nanosecond intervals since January 1, 1601
Make your math and use FileTimeToSystemTime to convert back
to a SYSTEMTIME struct.
'----
If you only want to add days, not fractions of days to a SYSTEMTIME
use SystemTimeToVariantTime and you will have the time in a double
where Integerpart is a day-number, and fraction is the time

------------------
Fred
mailto:[email protected][email protected]</A>
http://www.oxenby.se



[This message has been edited by Fred Oxenby (edited August 09, 2001).]

[Peter Lameijn]

mark,

see this:
http://www.powerbasic.com/support/pb...ad.php?t=23049

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peter.
mailto[email protected][email protected]</a>

[Errol Cheverie]

Mark
Hear is something I cobble together very quickly that illustrates
using Systemtime and Filetime API calls to to add and subtract days,
with very limited testing it seems to do what you're asking, hope
this helps.

Regards Errol


' For PBCC 2

#INCLUDE "WIN32API.INC"

%OneDay =  864000000000&&  ' 100-nanosecond increments in 1 day


' use our own type so we don't have to deal with a LARGE_INTEGER structure
TYPE MYFILETIME
    qFileTime AS QUAD
END TYPE

FUNCTION PBMAIN () AS LONG
LOCAL st AS SYSTEMTIME
LOCAL ft AS MYFILETIME

CALL GetLocalTime(ST)
PRINT "st.wYear :"; st.wYear
PRINT "st.wMonth:"; st.wMonth
PRINT "st.wDay  :"; st.wDay

CALL SystemTimeToFileTime(st, ft)
ft.qFileTime = ft.qFileTime + %OneDay

' ft.qFileTime = ft.qFileTime + %OneDay * 5 'to add 5 days
' ft.qFileTime = ft.qFileTime - %OneDay * 10 'to go back 10 days
' and so on

' convert back to SystemTime time structure
CALL FileTimeToSystemTime(ft, st)

PRINT
PRINT "After adding 1 day to date and time"

PRINT "st.wYear :"; st.wYear
PRINT "st.wMonth:"; st.wMonth
PRINT "st.wDay  :"; st.wDay

WAITKEY$
END FUNCTION

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[Egbert Zijlema]

#COMPILE EXE
#INCLUDE "WIN32API.INC"
 
%NaturalDay = 24 * 60 * 60 * 10000000
 
GLOBAL st AS SYSTEMTIME
 
UNION LARGETIME
  ft AS FILETIME
  qt AS QUAD
END UNION
 
FUNCTION DayNumber(BYVAL year AS LONG, _
                   BYVAL month AS LONG, _
                   BYVAL day AS LONG) AS LONG
  LOCAL lt AS LARGETIME

  IF year < 1601 THEN                            ' not allowed by Windows
    FUNCTION = %FALSE
    EXIT FUNCTION
  END IF
  st.wYear = year
  st.wMonth = month
  st.wDay = day
  dummy& = SystemTimeToFileTime(st, lt.ft)
  FUNCTION = lt.qt \ %NaturalDay
END FUNCTION
 
FUNCTION NumToDate(num AS LONG, lpFormat AS ASCIIZ) AS STRING
  LOCAL lt AS LARGETIME, szText AS ASCIIZ * 255
  LOCAL dwFlags AS LONG

  lt.qt = num * %NaturalDay
  dummy& = FileTimeToSystemTime(lt.ft, st)
  dwFlags = VAL(lpFormat)
  IF dwFlags THEN lpFormat = ""
  GetDateFormat %LOCALE_USER_DEFAULT, dwFlags, st, BYCOPY lpFormat, szText, SIZEOF(szText)
  FUNCTION = szText
END FUNCTION
 
FUNCTION PBMain() AS LONG
  LOCAL szLongDate AS ASCIIZ * 64
  LOCAL ToDay AS LONG, YesterDay AS LONG
 
  GetLocalTime st
  GetLocaleInfo %LOCALE_USER_DEFAULT, %LOCALE_SLONGDATE, szLongDate, SIZEOF(szLongdate)
    
  ToDay = DayNumber( st.wYear, st.wMonth, st.wDay)
  IF ISFALSE(ToDay) THEN
    MSGBOX "Windows can not handle years before 1601", 16, "Error"
    EXIT FUNCTION
  END IF
  YesterDay = ToDay - 1
  msg$ = "Today: " + NumToDate(ToDay, szLongDate) + $CRLF + _
         "Yesterday: " + NumToDate(YesterDay, szLongDate)
  MSGBOX msg$, 64, "Substracting 1 day..."
END FUNCTION

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mailto:[email protected][email protected]</A>
www.basicguru.com/zijlema/

[mark smit]

Thanks Guys!


As it turns out I was only off by a few zeros.

I had:
1000 * 60 * 60 * 24 = 86,400,000

When I should have had:
1000000 * 60 * 60 * 24 = 864,000,000,000

It was the old miliseconds VS nanoseconds debate. Thanks again for all the help guys, When "the net" doesn't have it the PB Forums do

------------------
Cheers!

[This message has been edited by mark smit (edited August 10, 2001).]