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NAME

       ASN1_TIME_set, ASN1_TIME_adj, ASN1_TIME_check, ASN1_TIME_set_string, ASN1_TIME_print,
       ASN1_TIME_diff - ASN.1 Time functions

SYNOPSIS

        ASN1_TIME *ASN1_TIME_set(ASN1_TIME *s, time_t t);
        ASN1_TIME *ASN1_TIME_adj(ASN1_TIME *s, time_t t,
                                 int offset_day, long offset_sec);
        int ASN1_TIME_set_string(ASN1_TIME *s, const char *str);
        int ASN1_TIME_check(const ASN1_TIME *t);
        int ASN1_TIME_print(BIO *b, const ASN1_TIME *s);

        int ASN1_TIME_diff(int *pday, int *psec,
                           const ASN1_TIME *from, const ASN1_TIME *to);

DESCRIPTION

       The function ASN1_TIME_set() sets the ASN1_TIME structure s to the time represented by the
       time_t value t. If s is NULL a new ASN1_TIME structure is allocated and returned.

       ASN1_TIME_adj() sets the ASN1_TIME structure s to the time represented by the time
       offset_day and offset_sec after the time_t value t.  The values of offset_day or
       offset_sec can be negative to set a time before t. The offset_sec value can also exceed
       the number of seconds in a day. If s is NULL a new ASN1_TIME structure is allocated and
       returned.

       ASN1_TIME_set_string() sets ASN1_TIME structure s to the time represented by string str
       which must be in appropriate ASN.1 time format (for example YYMMDDHHMMSSZ or
       YYYYMMDDHHMMSSZ).

       ASN1_TIME_check() checks the syntax of ASN1_TIME structure s.

       ASN1_TIME_print() prints out the time s to BIO b in human readable format. It will be of
       the format MMM DD HH:MM:SS YYYY [GMT], for example "Feb  3 00:55:52 2015 GMT" it does not
       include a newline. If the time structure has invalid format it prints out "Bad time value"
       and returns an error.

       ASN1_TIME_diff() sets *pday and *psec to the time difference between from and to. If to
       represents a time later than from then one or both (depending on the time difference) of
       *pday and *psec will be positive. If to represents a time earlier than from then one or
       both of *pday and *psec will be negative. If to and from represent the same time then
       *pday and *psec will both be zero.  If both *pday and *psec are non-zero they will always
       have the same sign. The value of *psec will always be less than the number of seconds in a
       day. If from or to is NULL the current time is used.

NOTES

       The ASN1_TIME structure corresponds to the ASN.1 structure Time defined in RFC5280 et al.
       The time setting functions obey the rules outlined in RFC5280: if the date can be
       represented by UTCTime it is used, else GeneralizedTime is used.

       The ASN1_TIME structure is represented as an ASN1_STRING internally and can be freed up
       using ASN1_STRING_free().

       The ASN1_TIME structure can represent years from 0000 to 9999 but no attempt is made to
       correct ancient calendar changes (for example from Julian to Gregorian calendars).

       Some applications add offset times directly to a time_t value and pass the results to
       ASN1_TIME_set() (or equivalent). This can cause problems as the time_t value can overflow
       on some systems resulting in unexpected results.  New applications should use
       ASN1_TIME_adj() instead and pass the offset value in the offset_sec and offset_day
       parameters instead of directly manipulating a time_t value.

BUGS

       ASN1_TIME_print() currently does not print out the time zone: it either prints out "GMT"
       or nothing. But all certificates complying with RFC5280 et al use GMT anyway.

EXAMPLES

       Set a time structure to one hour after the current time and print it out:

        #include <time.h>
        #include <openssl/asn1.h>
        ASN1_TIME *tm;
        time_t t;
        BIO *b;
        t = time(NULL);
        tm = ASN1_TIME_adj(NULL, t, 0, 60 * 60);
        b = BIO_new_fp(stdout, BIO_NOCLOSE);
        ASN1_TIME_print(b, tm);
        ASN1_STRING_free(tm);
        BIO_free(b);

       Determine if one time is later or sooner than the current time:

        int day, sec;

        if (!ASN1_TIME_diff(&day, &sec, NULL, to))
               /* Invalid time format */

        if (day > 0 || sec > 0)
          printf("Later\n");
        else if (day < 0 || sec < 0)
          printf("Sooner\n");
        else
          printf("Same\n");

RETURN VALUES

       ASN1_TIME_set() and ASN1_TIME_adj() return a pointer to an ASN1_TIME structure or NULL if
       an error occurred.

       ASN1_TIME_set_string() returns 1 if the time value is successfully set and 0 otherwise.

       ASN1_TIME_check() returns 1 if the structure is syntactically correct and 0 otherwise.

       ASN1_TIME_print() returns 1 if the time is successfully printed out and 0 if an error
       occurred (I/O error or invalid time format).

       ASN1_TIME_diff() returns 1 for success and 0 for failure. It can fail if the pass
       ASN1_TIME structure has invalid syntax for example.

COPYRIGHT

       Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.