HOWTO: Setting the System Date and Time Programmatically

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This article was previously published under Q188897

SUMMARY

Although the system date and time can be set manually from Control Panel, programatically changing these settings requires using the Win32 SetLocalTime function.

SetLocalTime is passed a SYSTEMTIME structure, containing the following members:

   WORD wYear
   WORD wMonth
   WORD wDayOfWeek
   WORD wDay
   WORD wHour
   WORD wMinute
   WORD wSecond
   WORD wMilliseconds

Similar to all structures, you must construct a string containing its proper memory representation. The Word2Str function in the code below performs this conversion.

Also, note that it is necessary to subtract 1 from the result of the FoxPro dow() function to obtain the wDayOfWeek member. Win32 treats Sunday as day 0 (zero) and Saturday as day 6, whereas dow() treats Sunday as day 1 and Saturday as day 7.

It is more convenient to use the SetLocalTime function rather than the intuitively more obvious choice, SetSystemTime, because the former treats the SYSTEMTIME structure as a timezone-adjusted local time, while the latter function treats the SYSTEMTIME structure as Greenwich Mean Time.

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MORE INFORMATION

Create and execute a program containing the code below. The program stores the current system date and time, changes it to 10:30:15.00 AM on 06/30/2001, displays the FoxPro time() and date() functions to demonstrate that the date and time have been changed, then resets them to their previous values.

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Sample Code

   SET CENTURY ON

   * Save the current date and time, reset it at the end.
   m.olddate = DATE()
   m.oldtime = TIME(1)

   * Set the system time arbitrarily to 10:30:15 AM on 06/30/2001.
   m.updtdate = {06/30/2001}
   m.updttime = "10:30:15.00"
   =setsystime(m.updtdate, m.updttime)

   =MESSAGEBOX("Old date: " + DTOC(m.olddate) + CHR(13) + ;
      "Old time: " + m.oldtime + CHR(13) + ;
      "New system date: " + DTOC(DATE()) + CHR(13) + ;
      "New system time: " + TIME(1), ;
      0 + 64 + 0, ;
      "SetLocalTime()")

   * Now, reset it to its original value.
   m.updtdate = m.olddate
   m.updttime = m.oldtime
   =setsystime(m.updtdate, m.updttime)


   * Function setsystime.
   * Parameters: date, character time in the form HH:MM:SS:hh.
   * Returns: nothing.
   FUNCTION setsystime

   PARAMETERS m.updtdate, m.updttime

   DECLARE SHORT SetLocalTime IN win32api STRING SystemTime

   * Use SendMessage to tell everybody that we've changed the system time.
   DECLARE INTEGER SendMessage IN win32api ;
      INTEGER WindowHandle, ;
      INTEGER MESSAGE, ;
      STRING Param1, ;
      STRING Param2

   * SendMessage constants.
   #DEFINE HWND_BROADCAST 65535
   #DEFINE WM_TIMECHANGE 30

   m.SystemTime = word2str(YEAR(m.updtdate)) + ;
      word2str(MONTH(m.updtdate)) + ;
      word2str(DOW(m.updtdate) - 1) + ;
      word2str(DAY(m.updtdate)) + ;
      word2str(VAL(LEFT(m.updttime, 2))) + ;
      word2str(VAL(SUBSTR(m.updttime, 4, 2))) + ;
      word2str(VAL(SUBSTR(m.updttime, 7, 2))) + ;
      word2str(VAL(RIGHT(m.updttime, 2)))

   m.retval = SetLocalTime(m.SystemTime)

   * Send the message that the time has changed.
   m.retval = SendMessage(HWND_BROADCAST, WM_TIMECHANGE, "", "")

   * Function word2str.
   * Parameters: 16-bit value.
   * Returns: low-high format string for use in structures
   * requiring a WORD value.
   FUNCTION word2str

   PARAMETERS m.wordval

   PRIVATE i, m.retstr

   m.retstr = ""
   FOR i = 8 TO 0 STEP -8
      m.retstr = CHR(INT(m.wordval/(2^i))) + m.retstr
      m.wordval = MOD(m.wordval, (2^i))
   NEXT
   RETURN m.retstr

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