1ASN1_TIME_set(3) OpenSSL ASN1_TIME_set(3)
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6 ASN1_TIME_set, ASN1_TIME_adj, ASN1_TIME_check, ASN1_TIME_set_string,
7 ASN1_TIME_print, ASN1_TIME_diff - ASN.1 Time functions.
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10 ASN1_TIME *ASN1_TIME_set(ASN1_TIME *s, time_t t);
11 ASN1_TIME *ASN1_TIME_adj(ASN1_TIME *s, time_t t,
12 int offset_day, long offset_sec);
13 int ASN1_TIME_set_string(ASN1_TIME *s, const char *str);
14 int ASN1_TIME_check(const ASN1_TIME *t);
15 int ASN1_TIME_print(BIO *b, const ASN1_TIME *s);
16 int ASN1_TIME_diff(int *pday, int *psec,
18 const ASN1_TIME *from, const ASN1_TIME *to);
19
21 The function ASN1_TIME_set() sets the ASN1_TIME structure s to the time
22 represented by the time_t value t. If s is NULL a new ASN1_TIME
23 structure is allocated and returned.
24 ASN1_TIME_adj() sets the ASN1_TIME structure s to the time represented
26 by the time offset_day and offset_sec after the time_t value t. The
27 values of offset_day or offset_sec can be negative to set a time before
28 t. The offset_sec value can also exceed the number of seconds in a day.
29 If s is NULL a new ASN1_TIME structure is allocated and returned.
30 ASN1_TIME_set_string() sets ASN1_TIME structure s to the time
32 represented by string str which must be in appropriate ASN.1 time
33 format (for example YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ).
34 ASN1_TIME_check() checks the syntax of ASN1_TIME structure s.
36 ASN1_TIME_print() prints out the time s to BIO b in human readable
38 format. It will be of the format MMM DD HH:MM:SS YYYY [GMT], for
39 example "Feb 3 00:55:52 2015 GMT" it does not include a newline. If
40 the time structure has invalid format it prints out "Bad time value"
41 and returns an error.
42 ASN1_TIME_diff() sets *pday and *psec to the time difference between
44 from and to. If to represents a time later than from then one or both
45 (depending on the time difference) of *pday and *psec will be positive.
46 If to represents a time earlier than from then one or both of *pday and
47 *psec will be negative. If to and from represent the same time then
48 *pday and *psec will both be zero. If both *pday and *psec are non-
49 zero they will always have the same sign. The value of *psec will
50 always be less than the number of seconds in a day. If from or to is
51 NULL the current time is used.
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54 The ASN1_TIME structure corresponds to the ASN.1 structure Time defined
55 in RFC5280 et al. The time setting functions obey the rules outlined in
56 RFC5280: if the date can be represented by UTCTime it is used, else
57 GeneralizedTime is used.
58 The ASN1_TIME structure is represented as an ASN1_STRING internally and
60 can be freed up using ASN1_STRING_free().
61 The ASN1_TIME structure can represent years from 0000 to 9999 but no
63 attempt is made to correct ancient calendar changes (for example from
64 Julian to Gregorian calendars).
65 Some applications add offset times directly to a time_t value and pass
67 the results to ASN1_TIME_set() (or equivalent). This can cause problems
68 as the time_t value can overflow on some systems resulting in
69 unexpected results. New applications should use ASN1_TIME_adj()
70 instead and pass the offset value in the offset_sec and offset_day
71 parameters instead of directly manipulating a time_t value.
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74 ASN1_TIME_print() currently does not print out the time zone: it either
75 prints out "GMT" or nothing. But all certificates complying with
76 RFC5280 et al use GMT anyway.
77
79 Set a time structure to one hour after the current time and print it
80 out:
81 #include <time.h>
83 #include <openssl/asn1.h>
84 ASN1_TIME *tm;
85 time_t t;
86 BIO *b;
87 t = time(NULL);
88 tm = ASN1_TIME_adj(NULL, t, 0, 60 * 60);
89 b = BIO_new_fp(stdout, BIO_NOCLOSE);
90 ASN1_TIME_print(b, tm);
91 ASN1_STRING_free(tm);
92 BIO_free(b);
93 Determine if one time is later or sooner than the current time:
95 int day, sec;
97 if (!ASN1_TIME_diff(&day, &sec, NULL, to))
99 /* Invalid time format */
100 if (day > 0 || sec > 0)
102 printf("Later\n");
103 else if (day < 0 || sec < 0)
104 printf("Sooner\n");
105 else
106 printf("Same\n");
107
109 ASN1_TIME_set() and ASN1_TIME_adj() return a pointer to an ASN1_TIME
110 structure or NULL if an error occurred.
111 ASN1_TIME_set_string() returns 1 if the time value is successfully set
113 and 0 otherwise.
114 ASN1_TIME_check() returns 1 if the structure is syntactically correct
116 and 0 otherwise.
117 ASN1_TIME_print() returns 1 if the time is successfully printed out and
119 0 if an error occurred (I/O error or invalid time format).
120 ASN1_TIME_diff() returns 1 for sucess and 0 for failure. It can fail if
122 the pass ASN1_TIME structure has invalid syntax for example.
1231.0.2o 2020-08-01 ASN1_TIME_set(3)