4.3BSD-Reno/src/bin/date/date.1

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.\"     @(#)date.1	6.8 (Berkeley) 7/24/90
.\"
.Dd July 24, 1990
.Dt DATE 1
.Os BSD 4.4
.Sh NAME
.Nm date
.Nd Display or set date and time
.Sh SYNOPSIS
.Nm date
.Op Fl nu
.Op Fl d Ar dst
.Op Fl t Ar minutes_west
.Op yymmddhhmm [\&.ss]
.Sh DESCRIPTION
.Nm Date
displays today's date and time when invoked without
arguments.  Providing an argument will set the desired date;
only the superuser can set the date.
.Pp
Options are:
.Pp
.Tw Ds
.Tp Fl d
Set the kernel's values for daylight savings time.
If
.Ar dst
is non-zero, future calls
to
.Xr gettimeofday 2
will return a non-zero
.Ql tz_dsttime  .
.Tp Fl t
Set the kernel's values for minutes west of GMT.
.Ar Minutes_west
provides the number of minutes returned by future calls to
.Xr gettimeofday 2
in
.Ql tz_minuteswest  .
.Tp Fl u
Display or set the date in GMT (universal) time.
.Tp
.Pp
The canonical representation for setting the date and time:
.Dw Ds
.Dp Ar yy
Year in abbreviated form (.e.g 89 for 1989).
.Dp Ar mm
Numeric month.
A number from 01 to 12.
.Dp Ar dd
Day, a number from 01 to 31.
.Dp Ar hh
Hour, a number from 00 to 24.
.Dp Ar mm
Minutes, a number from 00 to 60.
.Dp Ar .ss
Seconds, a number from 00 to 60.
.Dp
The command:
.Pp
.Dl date 8506131627
.Pp
sets the date to June 13 1985, 4:27 PM.
.Pp
To reset today's time, the incantation can be shortened
to just the hours and minutes:
.Pp
.Dl date 1432
.Pp
sets the time to 2:32 PM, unaffecting the date.
.Pp
Providing a system stays running, date will handle
time changes for daylight/standards savings time and leap times.
.Pp
If
.Xr timed 8
is running to synchronize the clocks of machines in a local
area network,
.Nm date
sets the time globally on all those
machines unless the
.Fl n
option is given.
.Sh FILES
.Dw /var/log/messages
.Di L
.Dp Pa /var/log/wtmp
A record of date resets and time changes.
.Dp Pa /var/log/messages
A record of the name of the user
setting the time.
.Sh SEE ALSO
.Xr gettimeofday 2 ,
.Xr utmp 5 ,
.Xr timed 8
.br
.Em TSP:\ The\ Time\ Synchronization Protocol
.Em for UNIX 4.3BSD ,
R. Gusella
and\ S.\ Zatti
.Sh HISTORY
.Nm Date
appeared in Version 6 AT&T UNIX.
.Sh DIAGNOSTICS
Exit status is 0 on success, 1 on complete failure to set the date,
and 2 on successfully setting the local date but failing globally.
.Pp
Occasionally, when
.Xr timed
synchronizes the time on many hosts,
the setting of a new time value may require more than a few seconds.
On these occasions,
.Nm date
prints: `Network time being set'.
The message `Communication error with timed' occurs when the communication
between
.Nm date
and
.Xr timed
fails.
.Sh BUGS
The system attempts to keep the date in a format closely compatible
with VMS.  VMS, however, uses local time (rather than GMT) and does
not understand daylight-saving time.  Thus, if you use both UNIX
and VMS, VMS will be running on GMT.