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ASN1_TIME_set(3)                    OpenSSL                   ASN1_TIME_set(3)

       ASN1_TIME_check, ASN1_UTCTIME_check, ASN1_GENERALIZEDTIME_check,
       ASN1_TIME_set_string, ASN1_UTCTIME_set_string,
       ASN1_GENERALIZEDTIME_set_string, ASN1_TIME_set_string_X509,
       ASN1_TIME_normalize, ASN1_TIME_to_tm, ASN1_TIME_print,
       ASN1_UTCTIME_print, ASN1_GENERALIZEDTIME_print, ASN1_TIME_diff,
       ASN1_TIME_cmp_time_t, ASN1_UTCTIME_cmp_time_t, ASN1_TIME_compare,
       ASN1_TIME_to_generalizedtime - ASN.1 Time functions

       libcrypto, -lcrypto

        ASN1_TIME *ASN1_TIME_set(ASN1_TIME *s, time_t t);
        ASN1_UTCTIME *ASN1_UTCTIME_set(ASN1_UTCTIME *s, time_t t);
                                                       time_t t);

        ASN1_TIME *ASN1_TIME_adj(ASN1_TIME *s, time_t t, int offset_day,
                                 long offset_sec);
        ASN1_UTCTIME *ASN1_UTCTIME_adj(ASN1_UTCTIME *s, time_t t,
                                       int offset_day, long offset_sec);
                                                       time_t t, int offset_day,
                                                       long offset_sec);

        int ASN1_TIME_set_string(ASN1_TIME *s, const char *str);
        int ASN1_TIME_set_string_X509(ASN1_TIME *s, const char *str);
        int ASN1_UTCTIME_set_string(ASN1_UTCTIME *s, const char *str);
                                            const char *str);

        int ASN1_TIME_normalize(ASN1_TIME *s);

        int ASN1_TIME_check(const ASN1_TIME *t);
        int ASN1_UTCTIME_check(const ASN1_UTCTIME *t);

        int ASN1_TIME_print(BIO *b, const ASN1_TIME *s);
        int ASN1_UTCTIME_print(BIO *b, const ASN1_UTCTIME *s);
        int ASN1_GENERALIZEDTIME_print(BIO *b, const ASN1_GENERALIZEDTIME *s);

        int ASN1_TIME_to_tm(const ASN1_TIME *s, struct tm *tm);
        int ASN1_TIME_diff(int *pday, int *psec, const ASN1_TIME *from,
                           const ASN1_TIME *to);

        int ASN1_TIME_cmp_time_t(const ASN1_TIME *s, time_t t);
        int ASN1_UTCTIME_cmp_time_t(const ASN1_UTCTIME *s, time_t t);

        int ASN1_TIME_compare(const ASN1_TIME *a, const ASN1_TIME *b);

        ASN1_GENERALIZEDTIME *ASN1_TIME_to_generalizedtime(ASN1_TIME *t,
                                                           ASN1_GENERALIZEDTIME **out);

       The ASN1_TIME_set(), ASN1_UTCTIME_set() and ASN1_GENERALIZEDTIME_set()
       functions set the structure s to the time represented by the time_t
       value t. If s is NULL a new time structure is allocated and returned.

       The ASN1_TIME_adj(), ASN1_UTCTIME_adj() and ASN1_GENERALIZEDTIME_adj()
       functions set the 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 structure is allocated and returned.

       The ASN1_TIME_set_string(), ASN1_UTCTIME_set_string() and
       ASN1_GENERALIZEDTIME_set_string() functions set the time structure s to
       the time represented by string str which must be in appropriate ASN.1
       time format (for example YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ). If s is
       NULL this function performs a format check on str only. The string str
       is copied into s.

       ASN1_TIME_set_string_X509() sets ASN1_TIME structure s to the time
       represented by string str which must be in appropriate time format that
       RFC 5280 requires, which means it only allows YYMMDDHHMMSSZ and
       YYYYMMDDHHMMSSZ (leap second is rejected), all other ASN.1 time format
       are not allowed. If s is NULL this function performs a format check on
       str only.

       The ASN1_TIME_normalize() function converts an ASN1_GENERALIZEDTIME or
       ASN1_UTCTIME into a time value that can be used in a certificate. It
       should be used after the ASN1_TIME_set_string() functions and before
       ASN1_TIME_print() functions to get consistent (i.e. GMT) results.

       The ASN1_TIME_check(), ASN1_UTCTIME_check() and
       ASN1_GENERALIZEDTIME_check() functions check the syntax of the time
       structure s.

       The ASN1_TIME_print(), ASN1_UTCTIME_print() and
       ASN1_GENERALIZEDTIME_print() functions print the time structure 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. The output for generalized
       time may include a fractional part following the second.

       ASN1_TIME_to_tm() converts the time s to the standard tm structure.  If
       s is NULL, then the current time is converted. The output time is GMT.
       The tm_sec, tm_min, tm_hour, tm_mday, tm_wday, tm_yday, tm_mon and
       tm_year fields of tm structure are set to proper values, whereas all
       other fields are set to 0. If tm is NULL this function performs a
       format check on s only. If s is in Generalized format with fractional
       seconds, e.g. YYYYMMDDHHMMSS.SSSZ, the fractional seconds will be lost
       while converting s to tm structure.

       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 nonzero
       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.

       The ASN1_TIME_cmp_time_t() and ASN1_UTCTIME_cmp_time_t() functions
       compare the two times represented by the time structure s and the
       time_t t.

       The ASN1_TIME_compare() function compares the two times represented by
       the time structures a and b.

       The ASN1_TIME_to_generalizedtime() function converts an ASN1_TIME to an
       ASN1_GENERALIZEDTIME, regardless of year. If either out or *out are
       NULL, then a new object is allocated and must be freed after use.

       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, ASN1_UTCTIME and ASN1_GENERALIZEDTIME structures are
       represented as an ASN1_STRING internally and can be freed up using

       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).

       ASN1_UTCTIME is limited to a year range of 1950 through 2049.

       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.

       ASN1_TIME_adj() may change the type from ASN1_GENERALIZEDTIME to
       ASN1_UTCTIME, or vice versa, based on the resulting year. The
       ASN1_GENERALIZEDTIME_adj() and ASN1_UTCTIME_adj() functions will not
       modify the type of the return structure.

       It is recommended that functions starting with ASN1_TIME be used
       instead of those starting with ASN1_UTCTIME or ASN1_GENERALIZEDTIME.
       The functions starting with ASN1_UTCTIME and ASN1_GENERALIZEDTIME act
       only on that specific time format. The functions starting with
       ASN1_TIME will operate on either format.

       ASN1_TIME_print(), ASN1_UTCTIME_print() and
       ASN1_GENERALIZEDTIME_print() do not print out the timezone: it either
       prints out "GMT" or nothing. But all certificates complying with
       RFC5280 et al use GMT anyway.

       Use the ASN1_TIME_normalize() function to normalize the time value
       before printing to get GMT results.

       ASN1_TIME_set(), ASN1_UTCTIME_set(), ASN1_GENERALIZEDTIME_set(),
       ASN1_TIME_adj(), ASN1_UTCTIME_adj and ASN1_GENERALIZEDTIME_set return a
       pointer to a time structure or NULL if an error occurred.

       ASN1_TIME_set_string(), ASN1_UTCTIME_set_string(),
       ASN1_GENERALIZEDTIME_set_string() ASN1_TIME_set_string_X509() return 1
       if the time value is successfully set and 0 otherwise.

       ASN1_TIME_normalize() returns 1 on success, and 0 on error.

       ASN1_TIME_check(), ASN1_UTCTIME_check and ASN1_GENERALIZEDTIME_check()
       return 1 if the structure is syntactically correct and 0 otherwise.

       ASN1_TIME_print(), ASN1_UTCTIME_print() and
       ASN1_GENERALIZEDTIME_print() return 1 if the time is successfully
       printed out and 0 if an error occurred (I/O error or invalid time

       ASN1_TIME_to_tm() returns 1 if the time is successfully parsed and 0 if
       an error occurred (invalid time format).

       ASN1_TIME_diff() returns 1 for success and 0 for failure. It can fail
       if the passed-in time structure has invalid syntax, for example.

       ASN1_TIME_cmp_time_t() and ASN1_UTCTIME_cmp_time_t() return -1 if s is
       before t, 0 if s equals t, or 1 if s is after t. -2 is returned on

       ASN1_TIME_compare() returns -1 if a is before b, 0 if a equals b, or 1
       if a is after b. -2 is returned on error.

       ASN1_TIME_to_generalizedtime() returns a pointer to the appropriate
       time structure on success or NULL if an error occurred.

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

        #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);

       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)
        else if (day < 0 || sec < 0)

       The ASN1_TIME_to_tm() function was added in OpenSSL 1.1.1.  The
       ASN1_TIME_set_string_X509() function was added in OpenSSL 1.1.1.  The
       ASN1_TIME_normalize() function was added in OpenSSL 1.1.1.  The
       ASN1_TIME_cmp_time_t() function was added in OpenSSL 1.1.1.  The
       ASN1_TIME_compare() function was added in OpenSSL 1.1.1.

       Copyright 2015-2020 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

1.1.1i                            2020-12-10                  ASN1_TIME_set(3)