.TH caltime 3
.SH NAME
caltime_tai \- convert calendar dates and times
.SH SYNTAX
.B #include <caltime.h>
.br
.B #include <tai.h>

void \fBcaltime_tai\fP(&\fIct\fR,&\fIt\fR);
.br
void \fBcaltime_utc\fP(&\fIct\fR,&\fIt\fR,&\fIweekday\fR,&\fIyearday\fR);

struct caltime \fIct\fR;
.br
struct tai \fIt\fR;
.br
int *\fIweekday\fR;
.br
int *\fIyearday\fR;
.SH DESCRIPTION
.B caltime_tai
reads a date, time, and UTC offset from
.IR ct .
It puts the corresponding TAI64 label into
.IR t .

.B caltime_utc
reads a TAI64 label from
.IR t .
It puts the corresponding date and time into
.IR ct ,
with UTC offset 0.

.B caltime_utc
fills in
.I weekday
and
.I yearday
the same way as
.BR caldate_frommjd .
.SH LIMITATIONS
The sequence of TAI64 labels has been determined
for the next few hundred billion years.
The same is not true, however, for
calendar dates and times.
New leap seconds are added every year or two,
as discussed in
.BR leapsecs (3);
and the Gregorian calendar will change in a few thousand years,
as discussed in
.BR caldate_mjd (3).
This means that
.B caltime_tai
and
.B caltime_utc
are not useful for dates far in the future.
.SH "SEE ALSO"
caldate_mjd(3),
caltime(3),
tai(3),
leapsecs(3)