example_confirming_strptime_is_consistent.c

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

int parse(const char* timestamp_as_string) {
  struct tm struct_tm;
  time_t t;
  memset(&struct_tm, 0, sizeof(struct tm));
  if (strptime(timestamp_as_string, "%m/%d/%Y %H:%M", &struct_tm)) {
    printf("strptime() returned `%d/%02d/%02d %02d:%02d:%02d; is_dst = %d`, ",
           struct_tm.tm_year + 1900,
           struct_tm.tm_mon,
           struct_tm.tm_mday,
           struct_tm.tm_hour,
           struct_tm.tm_min,
           struct_tm.tm_sec,
           struct_tm.tm_isdst);
    struct_tm.tm_isdst = -1;
    t = mktime(&struct_tm);
    printf("mktime() returned `%d`.\n", (int)t);
    return (int)t;
  } else {
    fprintf(stderr, "Failed to parse date: `%s`.\n", timestamp_as_string);
    return 0;
  }
}

int main() {
  const char* timestamp_of_interest = "11/06/2016 01:00";

  const char* previous_call_one = "11/06/2016 0:00";
  const char* previous_call_two = "11/06/2016 2:00";

  int t1;
  int t2;

  parse(previous_call_one);
  t1 = parse(timestamp_of_interest);

  parse(previous_call_two);
  t2 = parse(timestamp_of_interest);

  if (t1 == t2) {
    printf("OK\n");
  } else {
    printf("`%s` : %d != %d\n", timestamp_of_interest, t1, t2);
  }
}