#include <stdio.h>
#include <windows.h>
#include <timezoneapi.h>
#include <wchar.h>

/* Cf. <https://ss64.com/timezones.html>  */
# define FRENCH_TZ  "Romance Standard Time"

int main ()
{
  _putenv ("TZ=" FRENCH_TZ);

  DWORD ret;

  TIME_ZONE_INFORMATION info1;
  ret = GetTimeZoneInformation (&info1);
  printf ("GetTimeZoneInformation:\n"
          "ret = %lu  info1 =\n"
          "standard: |%ls| bias=%ld date=%4d-%02d-%02d %02d:%02d:%02d.%03d\n"
          "daylight: |%ls| bias=%ld date=%4d-%02d-%02d %02d:%02d:%02d.%03d\n",
          ret,
          info1.StandardName,
          info1.StandardBias,
          info1.StandardDate.wYear,
          info1.StandardDate.wMonth,
          info1.StandardDate.wDay,
          info1.StandardDate.wHour,
          info1.StandardDate.wMinute,
          info1.StandardDate.wSecond,
          info1.StandardDate.wMilliseconds,
          info1.DaylightName,
          info1.DaylightBias,
          info1.DaylightDate.wYear,
          info1.DaylightDate.wMonth,
          info1.DaylightDate.wDay,
          info1.DaylightDate.wHour,
          info1.DaylightDate.wMinute,
          info1.DaylightDate.wSecond,
          info1.DaylightDate.wMilliseconds);

  DYNAMIC_TIME_ZONE_INFORMATION info2;
  ret = GetDynamicTimeZoneInformation (&info2);
  printf ("GetDynamicTimeZoneInformation:\n"
          "ret = %lu  info2 = bias=%ld timezonekey=%ls dynamicdisabled=%d\n"
          "standard: |%ls| bias=%ld date=%4d-%02d-%02d %02d:%02d:%02d.%03d\n"
          "daylight: |%ls| bias=%ld date=%4d-%02d-%02d %02d:%02d:%02d.%03d\n",
          ret,
          info2.Bias,
          info2.TimeZoneKeyName,
          info2.DynamicDaylightTimeDisabled,
          info2.StandardName,
          info2.StandardBias,
          info2.StandardDate.wYear,
          info2.StandardDate.wMonth,
          info2.StandardDate.wDay,
          info2.StandardDate.wHour,
          info2.StandardDate.wMinute,
          info2.StandardDate.wSecond,
          info2.StandardDate.wMilliseconds,
          info2.DaylightName,
          info2.DaylightBias,
          info2.DaylightDate.wYear,
          info2.DaylightDate.wMonth,
          info2.DaylightDate.wDay,
          info2.DaylightDate.wHour,
          info2.DaylightDate.wMinute,
          info2.DaylightDate.wSecond,
          info2.DaylightDate.wMilliseconds);

  DYNAMIC_TIME_ZONE_INFORMATION info3i;
  TIME_ZONE_INFORMATION info3;
  {
    DWORD i;
    for (i = 0; ; i++)
      {
        if (EnumDynamicTimeZoneInformation (i, &info3i) == ERROR_SUCCESS // Link error in mingw, OK in MSVC.
            && wcscmp (info3i.TimeZoneKeyName, L"Romance Standard Time") == 0)
          break;
      }
  }
  ret = GetTimeZoneInformationForYear (2007, &info3i, &info3);
  printf ("GetTimeZoneInformationForYear(2007):\n"
          "ret = %lu  info3 =\n"
          "standard: |%ls| bias=%ld date=%4d-%02d-%02d %02d:%02d:%02d.%03d\n"
          "daylight: |%ls| bias=%ld date=%4d-%02d-%02d %02d:%02d:%02d.%03d\n",
          ret,
          info3.StandardName,
          info3.StandardBias,
          info3.StandardDate.wYear,
          info3.StandardDate.wMonth,
          info3.StandardDate.wDay,
          info3.StandardDate.wHour,
          info3.StandardDate.wMinute,
          info3.StandardDate.wSecond,
          info3.StandardDate.wMilliseconds,
          info3.DaylightName,
          info3.DaylightBias,
          info3.DaylightDate.wYear,
          info3.DaylightDate.wMonth,
          info3.DaylightDate.wDay,
          info3.DaylightDate.wHour,
          info3.DaylightDate.wMinute,
          info3.DaylightDate.wSecond,
          info3.DaylightDate.wMilliseconds);

}
/* Compile:
   $CC tzi.c -Wall -D_WIN32_WINNT=_WIN32_WINNT_WIN8 -ladvapi32
 */
/* Results:

GetTimeZoneInformation:
ret = 1  info1 =
standard: |W. Europe Standard Time| bias=0 date=   0-10-05 03:00:00.000
daylight: |W. Europe Daylight Time| bias=-60 date=   0-03-05 02:00:00.000
GetDynamicTimeZoneInformation:
ret = 1  info2 = bias=-60 timezonekey=W. Europe Standard Time dynamicdisabled=0
standard: |W. Europe Standard Time| bias=0 date=   0-10-05 03:00:00.000
daylight: |W. Europe Daylight Time| bias=-60 date=   0-03-05 02:00:00.000
GetTimeZoneInformationForYear(2007):
ret = 1  info3 =
standard: |Romance Standard Time| bias=0 date=   0-10-05 03:00:00.000
daylight: |Romance Daylight Time| bias=-60 date=   0-03-05 02:00:00.000

*/