UTC to local time converter in C++

Recently it was needed to convert UTC time string to local computer time string in C++ code. After analyzing several examples from stackoverflow and other resources I implemented this one. It is short application free from explicitely specified time zone. It is not extremely sophisticated at all. I am keeping it here mainly for my personal use, may be in future I will need to do it again, so I have working example to copy from and paste it somewhere. The code is below:

#include <stdio.h>

#include <sys/times.h>

#include <time.h>

#include <string.h>
int main(int argc, char * argv[])
{
   if(argc<2)
   {
      printf("Specify UTI time in the followin format: YYYY-MM-DAY HH:MM:SS\n");
      return -1;
   }
   char   szBuffer[32];
   struct tm tmstr;
   struct tm * tmlocal;
   time_t tslastutc;
   time_t tslastloc;
   memset(&tmstr, 0, sizeof(tm));
   strptime(argv[1], "%Y-%m-%d %H:%M:%S", &tmstr); // convert argument to struct tm
   memset(&szBuffer, 0, sizeof(szBuffer));
   strftime(szBuffer, sizeof(szBuffer), "%Y-%m-%d %H:%M:%S", &tmstr); // convert struct tm to string
   printf("UTC date and time: %s\n", szBuffer);
   tslastutc = timegm(&tmstr);     // get UCT Unix time from argument string time
   tslastloc = mktime(&tmstr);     // get local Unix time from argument string time
   tslastloc += tslastutc - tslastloc;
   tmlocal = localtime (&tslastloc);
   memset(&szBuffer, 0, sizeof(szBuffer));
   strftime(szBuffer, sizeof(szBuffer), "%Y-%m-%d %H:%M:%S", tmlocal); // convert local struct tm to string
   printf("Local date and time: %s\n", szBuffer);
   return 0;
}

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