Microsoft KB Archive/194576

= How To Obtain Time Zone Information in Visual FoxPro =

Article ID: 194576

Article Last Modified on 1/23/2007

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APPLIES TO


 * Microsoft Visual FoxPro 3.0 Standard Edition
 * Microsoft Visual FoxPro 3.0b Standard Edition
 * Microsoft Visual FoxPro 5.0 Standard Edition
 * Microsoft Visual FoxPro 5.0a
 * Microsoft Visual FoxPro 6.0 Professional Edition

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This article was previously published under Q194576



SUMMARY
Use the GetTimeZoneInformation API call to obtain information about the time zone, including the date and time when Daylight Saving 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 Saving Time status.



MORE INFORMATION
When the following program is executed, it displays two message boxes. The first displays the current Daylight Saving Time status, either TIME_ZONE_ID_STANDARD if Standard Time is in effect, or TIME_ZONE_ID_DAYLIGHT if Daylight Saving Time is in effect.

When you click OK, the second message box is displayed and includes the following seven items:

  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  The string description of Standard Time in the current time zone. For example, in the eastern time zone, this string is "Eastern Standard Time." 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. The bias, in minutes, to be used during local time translations that occur during Standard Time. For most time zones, this value is 0. The string description of Daylight Saving Time in the current time zone. For example, in the eastern time zone, this string is "Eastern Daylight Time." The month, day and time when Daylight Saving Time goes into effect. As above, the year portion of the date appears to be blank in all cases. The Daylight Saving Time bias, in minutes, used during local time translations that occur during daylight time. For most time zones, this value is -60.</li></ol>

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))

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")
 * format the standard time date for display

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 saving 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

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