generating ISO 8601 dates on win32 vs on anything else

iso8601.c

/**
 * released under http://unlicense.org/
 */

#include <time.h>

#ifdef _WIN32
#include <windows.h>

static void
gen_datetime(yajl_gen gen, time_t whence)
{
	int tz_bias, tz_hours, tz_minutes;
	TIME_ZONE_INFORMATION tzi;
	char buf[25];
	struct tm lt;
	size_t len;

	switch(GetTimeZoneInformation(&tzi)) {
	case TIME_ZONE_ID_STANDARD:
		tz_bias = tzi.Bias + tzi.StandardBias;
		break;

	case TIME_ZONE_ID_DAYLIGHT:
		tz_bias = tzi.Bias + tzi.DaylightBias;
		break;

	default:
		tz_bias = tzi.Bias;
		break;
	}

	tz_bias    = -tz_bias;
	tz_hours   = tz_bias / 60;
	tz_minutes = tz_bias % 60;

	localtime_s(&lt, &whence);
	len = strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S", &lt);

	if (len > sizeof(buf) - 6) {
		yajl_gen_integer(gen, whence);
		return;
	}

	buf[len++] = (tz_hours > 0) ? '+' : '-';
	sprintf_s(&buf[len], 4, "%02d%02d", abs(tz_hours), abs(tz_minutes));
	len += 4;

	yajl_gen_string(gen, (uint8_t *) buf, len);
}
#else
static void
gen_datetime(yajl_gen gen, time_t whence)
{
	char buf[25];
	struct tm lt;
	size_t len;

	localtime_r(&whence, &lt);
	len = strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S%z", &lt);

	yajl_gen_string(gen, (uint8_t *) buf, len);
}
#endif

"but will," you say, "windows clearly supports strftime, why do you need all that extra bullshit?" my dear friend, it is chiefly the fault of the %z format spec. my format string (%z included) looks like this on linux:

"2014-02-10T22:29:46+0100"

and this on win32:

"2014-02-10T21:47:04Central Europe Standard Time"

thanks microsoft

but that's my fav feature of strftime, wai u tryna remove it