#include <string.h>
        #include <stdlib.h>
        #include <stdio.h>
        #include <time.h>
        #include <locale.h>
        #include <errno.h>

        #define NUM_OF_DATES  7
        #define BUF_SIZE 256

        /* This program takes a number of date and time strings and     */
        /* converts them into tm structs using strptime().  These tm    */
        /* structs are then passed to strftime() which will reverse the */
        /* process.  The resulting strings are then compared with the   */
        /* originals and if a difference is found then an error is      */
        /* displayed.                                                   */

        main()
        {
        int count,
            i;
        char buffer[BUF_SIZE];
        char *ret_val;
        struct tm time_struct;
        char dates[NUM_OF_DATES][BUF_SIZE] =
        {
            "Thursday 01 January 1970 00:08:20",
            "Tuesday 29 February 1972 08:26:40",
            "Tuesday 31 December 1991 23:59:59",
            "Wednesday 01 January 1992 00:00:00",
            "Sunday 03 May 1992 13:33:20",
            "Monday 04 May 1992 17:20:00",
            "Friday 15 May 1992 03:20:00"};

        for (i = 0; i < NUM_OF_DATES; i++) {
            /* Convert to a tm structure */
         ret_val = strptime(dates[i], "%A %d %B %Y %T", &time_struct);

            /* Check the return value */
            if (ret_val == (char *) NULL) {
                perror("strptime");
                exit(EXIT_FAILURE);
            }

            /* Convert the time structure back to a formatted string */
        count = strftime(buffer, BUF_SIZE, "%A %d %B %Y %T",&time_struct);

            /* Check the return value */
            if (count == 0) {
                perror("strftime");
                exit(EXIT_FAILURE);
            }

            /* Check the result */
            if (strcmp(buffer, dates[i]) != 0) {
            printf("Error: Converted string differs from the original\n");
            }
            else {
                printf("Successfully converted <%s>\n", dates[i]);
            }
         }
        }

    Running the example program produces the following result:

    Successfully converted <Thursday 01 January 1970 00:08:20>
    Successfully converted <Tuesday 29 February 1972 08:26:40>
    Successfully converted <Tuesday 31 December 1991 23:59:59>
    Successfully converted <Wednesday 01 January 1992 00:00:00>
    Successfully converted <Sunday 03 May 1992 13:33:20>
    Successfully converted <Monday 04 May 1992 17:20:00>
    Successfully converted <Friday 15 May 1992 03:20:00>