Q194576: HOWTO: Obtain Time Zone Information in Visual FoxPro
Article: Q194576
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Operating System(s):
Keyword(s):
Last Modified: 10-AUG-1999
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The information in this article applies to:
- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0
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SUMMARY
=======
Use the GetTimeZoneInformation API call to obtain information about the time
zone, including the date and time when Daylight Savings Time and Standard Time
take effect, the "bias," or time difference between the current time zone and
the Coordinated Universal Time, and the current Daylight Savings Time status.
MORE INFORMATION
================
When the following program is executed, it displays two message boxes. The first
displays the current Daylight Savings Time status, either TIME_ZONE_ID_STANDARD
if Standard Time is in effect, or TIME_ZONE_ID_DAYLIGHT if Daylight Savings Time
is in effect.
When you click OK, the second message box is displayed and includes the following
seven items:
1. The bias, in minutes, from Coordinated Universal Time (UTC). For the "Eastern
Time (US & Canada)" time zone, this will be 300. All translations between
UTC and local time are based on the following formula:
UTC = local time + bias
2. The string description of Standard Time in the current time zone. For
example, in the eastern time zone, this string is "Eastern Standard Time."
3. The month, day, and time when Standard Time goes into effect. The year
portion of the date appears to be blank in all cases. The time portion is
expressed as a military time.
4. The bias, in minutes, to be used during local time translations that occur
during Standard Time. For most time zones, this value is 0.
5. The string description of Daylight Savings Time in the current time zone. For
example, in the eastern time zone, this string is "Eastern Daylight Time."
6. The month, day and time when Daylight Savings Time goes into effect. As
above, the year portion of the date appears to be blank in all cases.
7. The Daylight Savings Time bias, in minutes, used during local time
translations that occur during daylight time. For most time zones, this value
is -60.
Save and execute the following program:
#DEFINE ID_INVALID -1
#DEFINE ID_UNKNOWN 0
#DEFINE ID_STANDARD 1
#DEFINE ID_DAYLIGHT 2
#DEFINE CR CHR(13)
* the definition for TIME_ZONE_INFORMATION is:
*
*typedef struct _TIME_ZONE_INFORMATION { // tzi
* LONG Bias;
* WCHAR StandardName[ 32 ];
* SYSTEMTIME StandardDate;
* LONG StandardBias;
* WCHAR DaylightName[ 32 ];
* SYSTEMTIME DaylightDate;
* LONG DaylightBias;
*} TIME_ZONE_INFORMATION;
* buffer to receive TIME_ZONE_INFORMATION
TZInfo = SPACE(172)
DECLARE INTEGER GetTimeZoneInformation IN kernel32 STRING @TZInfo
liRetCode = GetTimeZoneInformation(@TZInfo)
DO CASE
CASE liRetCode = ID_UNKNOWN
=MESSAGEBOX ("TIME_ZONE_ID_UNKNOWN")
CASE liRetCode = ID_STANDARD
=MESSAGEBOX ("TIME_ZONE_ID_STANDARD")
CASE liRetCode = ID_DAYLIGHT
=MESSAGEBOX ("TIME_ZONE_ID_DAYLIGHT")
ENDCASE
* now, parse the returned structure
liBias = StrToLong(SUBSTR(TZInfo, 1, 4))
* lcStandardName is a Unicode string - strip out chr(0)s for
* US/English
lcStandardName = SUBSTR(TZInfo, 5, 64)
lcStandardName = STRTRAN(lcStandardName, CHR(0), "")
* lcStandardDate is a SYSTEMTIME structure, defined as follows:
*
*typedef struct _SYSTEMTIME { // st
* WORD wYear;
* WORD wMonth;
* WORD wDayOfWeek;
* WORD wDay;
* WORD wHour;
* WORD wMinute;
* WORD wSecond;
* WORD wMilliseconds;
*} SYSTEMTIME;
* this SYSTEMTIME struct must be parsed again
lcStandardDate = SUBSTR(TZInfo, 69, 16)
lcSDYear = Str2Word(SUBSTR(lcStandardDate, 1, 2))
lcSDMonth = Str2Word(SUBSTR(lcStandardDate, 3, 2))
lcSDDayofWeek = Str2Word(SUBSTR(lcStandardDate, 5, 2))
lcSDDay = Str2Word(SUBSTR(lcStandardDate, 7, 2))
lcSDHour = Str2Word(SUBSTR(lcStandardDate, 9, 2))
lcSDMinute = Str2Word(SUBSTR(lcStandardDate, 11, 2))
lcSDSecond = Str2Word(SUBSTR(lcStandardDate, 13, 2))
lcSDMSec = Str2Word(SUBSTR(lcStandardDate, 15, 2))
* format the standard time date for display
lcStandardDate = PADL(LTRIM(STR(lcSDMonth, 2, 0)), 2, "0") + "/" + ;
PADL(LTRIM(STR(lcSDDay, 2, 0)), 2, "0") + "/" + ;
PADL(LTRIM(STR(lcSDYear, 2, 0)), 2, "0") + ;
" " + ;
PADL(LTRIM(STR(lcSDHour, 2, 0)), 2, "0") + ":" + ;
PADL(LTRIM(STR(lcSDMinute, 2, 0)), 2, "0") + ":" + ;
PADL(LTRIM(STR(lcSDSecond, 2, 0)), 2, "0") + "." + ;
PADL(LTRIM(STR(lcSDMSec, 3, 0)), 3, "0")
liStandardBias = StrToLong(SUBSTR(TZInfo, 85, 4))
* lcDaylightname is also a Unicode string
lcDaylightName = SUBSTR(TZInfo, 89, 64)
lcDaylightName = STRTRAN(lcDaylightName, CHR(0), "")
* this SYSTEMTIME struct must be parsed again, same as above
lcDaylightDate = SUBSTR(TZInfo, 153, 16)
lcDDYear = Str2Word(SUBSTR(lcDaylightDate, 1, 2))
lcDDMonth = Str2Word(SUBSTR(lcDaylightDate, 3, 2))
lcDDDayofWeek = Str2Word(SUBSTR(lcDaylightDate, 5, 2))
lcDDDay = Str2Word(SUBSTR(lcDaylightDate, 7, 2))
lcDDHour = Str2Word(SUBSTR(lcDaylightDate, 9, 2))
lcDDMinute = Str2Word(SUBSTR(lcDaylightDate, 11, 2))
lcDDSecond = Str2Word(SUBSTR(lcDaylightDate, 13, 2))
lcDDMSec = Str2Word(SUBSTR(lcDaylightDate, 15, 2))
* format the daylight date for display
lcDaylightDate = PADL(LTRIM(STR(lcDDMonth, 2, 0)), 2, "0") + "/" + ;
PADL(LTRIM(STR(lcDDDay, 2, 0)), 2, "0") + "/" + ;
PADL(LTRIM(STR(lcDDYear, 2, 0)), 2, "0") + ;
" " + ;
PADL(LTRIM(STR(lcDDHour, 2, 0)), 2, "0") + ":" + ;
PADL(LTRIM(STR(lcDDMinute, 2, 0)), 2, "0") + ":" + ;
PADL(LTRIM(STR(lcDDSecond, 2, 0)), 2, "0") + "." + ;
PADL(LTRIM(STR(lcDDMSec, 3, 0)), 3, "0")
* Daylight savings time bias is a negative value
* stored in 2s complement, so subtract 2^32 to obtain a decimal value
liDaylightBias = StrToLong(SUBSTR(TZInfo, 169, 4)) - 2 ^ 32
=MESSAGEBOX("Bias: " + LTRIM(STR(liBias)) + CR + ;
"Standard name: " + lcStandardName + CR + ;
"Standard date: " + lcStandardDate + CR + ;
"Standard bias: " + LTRIM(STR(liStandardBias)) + CR + ;
"Daylight name: " + lcDaylightName + CR + ;
"Daylight date: " + lcDaylightDate + CR + ;
"Daylight bias: " + LTRIM(STR(liDaylightBias)))
RETURN
******************
FUNCTION StrToLong
******************
* Passed: 4-byte character string (lcLongstr) in low-high ASCII format
* Returns: long integer value
* Example:
* m.longstr = "1111"
* m.longval = strtolong(m.longstr)
PARAMETERS lcLongstr
PRIVATE i, lnRetval
lnRetval = 0
FOR i = 0 TO 24 STEP 8
lnRetval = lnRetval + (ASC(lcLongstr) * (2^i))
lcLongstr = RIGHT(lcLongstr, LEN(lcLongstr) - 1)
NEXT
RETURN lnRetval
**********************
FUNCTION Str2Word
PARAMETERS m.wordstr
PRIVATE i, m.retval
m.retval = 0
FOR i = 0 TO 8 STEP 8
m.retval = m.retval + (ASC(m.wordstr) * (2^i))
m.wordstr = RIGHT(m.wordstr, LEN(m.wordstr) - 1)
NEXT
RETURN m.retval
REFERENCES
==========
Win32 API Helpfile
Additional query words: kbVFP600 kbvfp300b kbvfp500a
======================================================================
Keywords :
Technology : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version : WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Issue type : kbhowto
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