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.\"
.IX Title "ASN1_TIME_set 3"
.TH ASN1_TIME_set 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
ASN1_TIME_set, ASN1_TIME_adj, ASN1_TIME_check, ASN1_TIME_set_string,
ASN1_TIME_print, ASN1_TIME_diff \- ASN.1 Time functions.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 6
\& 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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The function \fIASN1_TIME_set()\fR sets the \s-1ASN1_TIME\s0 structure \fBs\fR to the
time represented by the time_t value \fBt\fR. If \fBs\fR is \s-1NULL\s0 a new \s-1ASN1_TIME\s0
structure is allocated and returned.
.PP
\&\fIASN1_TIME_adj()\fR sets the \s-1ASN1_TIME\s0 structure \fBs\fR to the time represented
by the time \fBoffset_day\fR and \fBoffset_sec\fR after the time_t value \fBt\fR.
The values of \fBoffset_day\fR or \fBoffset_sec\fR can be negative to set a
time before \fBt\fR. The \fBoffset_sec\fR value can also exceed the number of
seconds in a day. If \fBs\fR is \s-1NULL\s0 a new \s-1ASN1_TIME\s0 structure is allocated
and returned.
.PP
\&\fIASN1_TIME_set_string()\fR sets \s-1ASN1_TIME\s0 structure \fBs\fR to the time
represented by string \fBstr\fR which must be in appropriate \s-1ASN.1\s0 time
format (for example \s-1YYMMDDHHMMSSZ\s0 or \s-1YYYYMMDDHHMMSSZ\s0).
.PP
\&\fIASN1_TIME_check()\fR checks the syntax of \s-1ASN1_TIME\s0 structure \fBs\fR.
.PP
\&\fIASN1_TIME_print()\fR prints out the time \fBs\fR to \s-1BIO \s0\fBb\fR in human readable
format. It will be of the format \s-1MMM DD HH:MM:SS YYYY\s0 [\s-1GMT\s0], for example
\&\*(L"Feb  3 00:55:52 2015 \s-1GMT\*(R"\s0 it does not include a newline. If the time
structure has invalid format it prints out \*(L"Bad time value\*(R" and returns
an error.
.PP
\&\fIASN1_TIME_diff()\fR sets \fB*pday\fR and \fB*psec\fR to the time difference between
\&\fBfrom\fR and \fBto\fR. If \fBto\fR represents a time later than \fBfrom\fR then
one or both (depending on the time difference) of \fB*pday\fR and \fB*psec\fR
will be positive. If \fBto\fR represents a time earlier than \fBfrom\fR then
one or both of \fB*pday\fR and \fB*psec\fR will be negative. If \fBto\fR and \fBfrom\fR
represent the same time then \fB*pday\fR and \fB*psec\fR will both be zero.
If both \fB*pday\fR and \fB*psec\fR are non-zero they will always have the same
sign. The value of \fB*psec\fR will always be less than the number of seconds
in a day. If \fBfrom\fR or \fBto\fR is \s-1NULL\s0 the current time is used.
.SH "NOTES"
.IX Header "NOTES"
The \s-1ASN1_TIME\s0 structure corresponds to the \s-1ASN.1\s0 structure \fBTime\fR
defined in \s-1RFC5280\s0 et al. The time setting functions obey the rules outlined
in \s-1RFC5280:\s0 if the date can be represented by UTCTime it is used, else
GeneralizedTime is used.
.PP
The \s-1ASN1_TIME\s0 structure is represented as an \s-1ASN1_STRING\s0 internally and can
be freed up using \fIASN1_STRING_free()\fR.
.PP
The \s-1ASN1_TIME\s0 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).
.PP
Some applications add offset times directly to a time_t value and pass the
results to \fIASN1_TIME_set()\fR (or equivalent). This can cause problems as the
time_t value can overflow on some systems resulting in unexpected results.
New applications should use \fIASN1_TIME_adj()\fR instead and pass the offset value
in the \fBoffset_sec\fR and \fBoffset_day\fR parameters instead of directly
manipulating a time_t value.
.SH "BUGS"
.IX Header "BUGS"
\&\fIASN1_TIME_print()\fR currently does not print out the time zone: it either prints
out \*(L"\s-1GMT\*(R"\s0 or nothing. But all certificates complying with \s-1RFC5280\s0 et al use \s-1GMT\s0
anyway.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Set a time structure to one hour after the current time and print it out:
.PP
.Vb 11
\& #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);
.Ve
.PP
Determine if one time is later or sooner than the current time:
.PP
.Vb 1
\& int day, sec;
\&
\& if (!ASN1_TIME_diff(&day, &sec, NULL, to))
\&        /* Invalid time format */
\&
\& if (day > 0 || sec > 0)
\&   printf("Later\en");
\& else if (day < 0 || sec < 0)
\&   printf("Sooner\en");
\& else
\&   printf("Same\en");
.Ve
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIASN1_TIME_set()\fR and \fIASN1_TIME_adj()\fR return a pointer to an \s-1ASN1_TIME\s0 structure
or \s-1NULL\s0 if an error occurred.
.PP
\&\fIASN1_TIME_set_string()\fR returns 1 if the time value is successfully set and
0 otherwise.
.PP
\&\fIASN1_TIME_check()\fR returns 1 if the structure is syntactically correct and 0
otherwise.
.PP
\&\fIASN1_TIME_print()\fR returns 1 if the time is successfully printed out and 0 if
an error occurred (I/O error or invalid time format).
.PP
\&\fIASN1_TIME_diff()\fR returns 1 for sucess and 0 for failure. It can fail if the
pass \s-1ASN1_TIME\s0 structure has invalid syntax for example.