Example of how to work with timezones in C

timezone-test.c

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

int main( int argc, char* argv[] )
{
	char buffer[ 128 ];
	time_t now = time(NULL);
	const char* time_str = "";

	setenv( "TZ", "Asia/Kolkata", 1 );
	tzset();
	time_str = asctime( localtime(&now) );
	strftime( buffer, sizeof(buffer),  "%z", localtime(&now) );
	printf( "Asia/Kolkata %s  %s", buffer, time_str );

	setenv( "TZ", "America/New_York", 1 );
	tzset();
	time_str = asctime( localtime(&now) );
	strftime( buffer, sizeof(buffer),  "%z", localtime(&now) );
	printf( "America/New_York %s  %s", buffer, time_str );

	setenv( "TZ", "Australia/Brisbane", 1 );
	tzset();
	time_str = asctime( localtime(&now) );
	strftime( buffer, sizeof(buffer),  "%z", localtime(&now) );
	printf( "Australia/Brisbane %s  %s", buffer, time_str );


	return 0;
}