1=pod
2
3=head1 NAME
4
5ASN1_TIME_set, ASN1_TIME_adj, ASN1_TIME_check, ASN1_TIME_set_string,
6ASN1_TIME_print, ASN1_TIME_diff - ASN.1 Time functions.
7
8=head1 SYNOPSIS
9
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
17 int ASN1_TIME_diff(int *pday, int *psec,
18                    const ASN1_TIME *from, const ASN1_TIME *to);
19
20=head1 DESCRIPTION
21
22The function ASN1_TIME_set() sets the ASN1_TIME structure B<s> to the
23time represented by the time_t value B<t>. If B<s> is NULL a new ASN1_TIME
24structure is allocated and returned.
25
26ASN1_TIME_adj() sets the ASN1_TIME structure B<s> to the time represented
27by the time B<offset_day> and B<offset_sec> after the time_t value B<t>.
28The values of B<offset_day> or B<offset_sec> can be negative to set a
29time before B<t>. The B<offset_sec> value can also exceed the number of
30seconds in a day. If B<s> is NULL a new ASN1_TIME structure is allocated
31and returned.
32
33ASN1_TIME_set_string() sets ASN1_TIME structure B<s> to the time
34represented by string B<str> which must be in appropriate ASN.1 time
35format (for example YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ).
36
37ASN1_TIME_check() checks the syntax of ASN1_TIME structure B<s>.
38
39ASN1_TIME_print() prints out the time B<s> to BIO B<b> in human readable
40format. It will be of the format MMM DD HH:MM:SS YYYY [GMT], for example
41"Feb  3 00:55:52 2015 GMT" it does not include a newline. If the time
42structure has invalid format it prints out "Bad time value" and returns
43an error.
44
45ASN1_TIME_diff() sets B<*pday> and B<*psec> to the time difference between
46B<from> and B<to>. If B<to> represents a time later than B<from> then
47one or both (depending on the time difference) of B<*pday> and B<*psec>
48will be positive. If B<to> represents a time earlier than B<from> then
49one or both of B<*pday> and B<*psec> will be negative. If B<to> and B<from>
50represent the same time then B<*pday> and B<*psec> will both be zero.
51If both B<*pday> and B<*psec> are non-zero they will always have the same
52sign. The value of B<*psec> will always be less than the number of seconds
53in a day. If B<from> or B<to> is NULL the current time is used.
54
55=head1 NOTES
56
57The ASN1_TIME structure corresponds to the ASN.1 structure B<Time>
58defined in RFC5280 et al. The time setting functions obey the rules outlined
59in RFC5280: if the date can be represented by UTCTime it is used, else
60GeneralizedTime is used.
61
62The ASN1_TIME structure is represented as an ASN1_STRING internally and can
63be freed up using ASN1_STRING_free().
64
65The ASN1_TIME structure can represent years from 0000 to 9999 but no attempt
66is made to correct ancient calendar changes (for example from Julian to
67Gregorian calendars).
68
69Some applications add offset times directly to a time_t value and pass the
70results to ASN1_TIME_set() (or equivalent). This can cause problems as the
71time_t value can overflow on some systems resulting in unexpected results.
72New applications should use ASN1_TIME_adj() instead and pass the offset value
73in the B<offset_sec> and B<offset_day> parameters instead of directly
74manipulating a time_t value.
75
76=head1 BUGS
77
78ASN1_TIME_print() currently does not print out the time zone: it either prints
79out "GMT" or nothing. But all certificates complying with RFC5280 et al use GMT
80anyway.
81
82=head1 EXAMPLES
83
84Set a time structure to one hour after the current time and print it out:
85
86 #include <time.h>
87 #include <openssl/asn1.h>
88 ASN1_TIME *tm;
89 time_t t;
90 BIO *b;
91 t = time(NULL);
92 tm = ASN1_TIME_adj(NULL, t, 0, 60 * 60);
93 b = BIO_new_fp(stdout, BIO_NOCLOSE);
94 ASN1_TIME_print(b, tm);
95 ASN1_STRING_free(tm);
96 BIO_free(b);
97
98Determine if one time is later or sooner than the current time:
99
100 int day, sec;
101
102 if (!ASN1_TIME_diff(&day, &sec, NULL, to))
103	/* Invalid time format */
104
105 if (day > 0 || sec > 0)
106   printf("Later\n");
107 else if (day < 0 || sec < 0)
108   printf("Sooner\n");
109 else
110   printf("Same\n");
111
112=head1 RETURN VALUES
113
114ASN1_TIME_set() and ASN1_TIME_adj() return a pointer to an ASN1_TIME structure
115or NULL if an error occurred.
116
117ASN1_TIME_set_string() returns 1 if the time value is successfully set and
1180 otherwise.
119
120ASN1_TIME_check() returns 1 if the structure is syntactically correct and 0
121otherwise.
122
123ASN1_TIME_print() returns 1 if the time is successfully printed out and 0 if
124an error occurred (I/O error or invalid time format).
125
126ASN1_TIME_diff() returns 1 for sucess and 0 for failure. It can fail if the
127pass ASN1_TIME structure has invalid syntax for example.
128
129=cut
130