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32 .\" @(#)date.1 8.3 (Berkeley) 4/28/95
40 .Nd display or set date and time
53 .Op Cm + Ns Ar output_fmt
57 .Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH
62 .Fl f Ar input_fmt new_date
63 .Op Cm + Ns Ar output_fmt
66 .Op Fl t Ar minutes_west
68 When invoked without arguments, the
70 utility displays the current date and time.
71 Otherwise, depending on the options specified,
73 will set the date and time or print it in a user-defined way.
77 utility displays the date and time read from the kernel clock.
78 When used to set the date and time,
79 both the kernel clock and the hardware clock are updated.
81 Only the superuser may set the date,
82 and if the system securelevel (see
85 the time may not be changed by more than 1 second.
87 The options are as follows:
90 Set the kernel's value for daylight saving time.
93 is non-zero, future calls
96 will return a non-zero for
101 as the format string to parse the
103 provided rather than using the default
114 Parsing is done using
117 Do not try to set the date.
118 This allows you to use the
120 flag in addition to the
122 option to convert one date format to another.
128 sets the time on all of the machines in the local group.
131 option suppresses this behavior and causes the time to be set only on the
134 Use RFC 2822 date and time output format. This is equivalent to use
135 .Dq Li %a, %d %b %Y \&%T %z
144 Print the date and time represented by
148 is the number of seconds since the Epoch
149 (00:00:00 UTC, January 1, 1970;
152 and can be specified in decimal, octal, or hex.
153 .It Fl t Ar minutes_west
154 Set the system's value for minutes west of
157 specifies the number of minutes returned in
162 Display or set the date in
164 (Coordinated Universal) time.
166 Adjust (i.e., take the current date and display the result of the
167 adjustment; not actually set the date) the second, minute, hour, month
168 day, week day, month or year according to
172 is preceded with a plus or minus sign,
173 the date is adjusted forwards or backwards according to the remaining string,
174 otherwise the relevant part of the date is set.
175 The date can be adjusted as many times as required using these flags.
176 Flags are processed in the order given.
179 (rather than adjusting them),
180 seconds are in the range 0-59, minutes are in the range 0-59, hours are
181 in the range 0-23, month days are in the range 1-31, week days are in the
183 months are in the range 1-12 (Jan-Dec)
184 and years are in the range 80-38 or 1980-2038.
188 is numeric, one of either
197 must be used to specify which part of the date is to be adjusted.
199 The week day or month may be specified using a name rather than a
201 If a name is used with the plus
203 sign, the date will be put forwards
207 date that matches the given week day or month.
208 This will not adjust the date,
209 if the given week day or month is the same as the current one.
211 When a date is adjusted to a specific value or in units greater than hours,
212 daylight savings time considerations are ignored.
213 Adjustments in units of hours or less honor daylight saving time.
214 So, assuming the current date is March 26, 0:30 and that the DST adjustment
215 means that the clock goes forward at 01:00 to 02:00, using
217 will adjust the date to March 26, 2:30.
218 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
219 the clock goes back at 02:00 to 01:00, using
221 will be necessary to reach October 29, 2:30.
223 When the date is adjusted to a specific value that does not actually exist
224 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
225 the date will be silently adjusted forwards in units of one hour until it
226 reaches a valid time.
227 When the date is adjusted to a specific value that occurs twice
228 (for example October 29, 1:30 2000),
229 the resulting timezone will be set so that the date matches the earlier of
232 It is not possible to adjust a date to an invalid absolute day, so using
234 .Fl v No 31d Fl v No 12m
235 will simply fail five months of the year.
236 It is therefore usual to set the month before setting the day; using
237 .Fl v No 12m Fl v No 31d
240 Adjusting the date by months is inherently ambiguous because
241 a month is a unit of variable length depending on the current date.
242 This kind of date adjustment is applied in the most intuitive way.
245 tries to preserve the day of the month.
246 If it is impossible because the target month is shorter than the present one,
247 the last day of the target month will be the result.
250 on May 31 will adjust the date to June 30, while using the same option
251 on January 30 will result in the date adjusted to the last day of February.
252 This approach is also believed to make the most sense for shell scripting.
253 Nevertheless, be aware that going forth and back by the same number of
254 months may take you to a different date.
256 Refer to the examples below for further details.
259 An operand with a leading plus
261 sign signals a user-defined format string
262 which specifies the format in which to display the date and time.
263 The format string may contain any of the conversion specifications
266 manual page, as well as any arbitrary text.
269 character is always output after the characters specified by
271 The format string for the default display is
274 If an operand does not have a leading plus sign, it is interpreted as
275 a value for setting the system's notion of the current date and time.
276 The canonical representation for setting the date and time is:
278 .Bl -tag -width Ds -compact -offset indent
282 prepended to the abbreviated year.
284 Year in abbreviated form
285 (e.g., 89 for 1989, 06 for 2006).
287 Numeric month, a number from 1 to 12.
289 Day, a number from 1 to 31.
291 Hour, a number from 0 to 23.
293 Minutes, a number from 0 to 59.
295 Seconds, a number from 0 to 61
296 (59 plus a maximum of two leap seconds).
299 Everything but the minutes is optional.
301 Time changes for Daylight Saving Time, standard time, leap seconds,
302 and leap years are handled automatically.
304 The following environment variables affect the execution of
308 The timezone to use when displaying dates.
309 The normal format is a pathname relative to
310 .Pa /usr/share/zoneinfo .
311 For example, the command
312 .Dq TZ=America/Los_Angeles date
313 displays the current time in California.
316 for more information.
319 .Bl -tag -width /var/log/messages -compact
320 .It Pa /var/log/utx.log
321 record of date resets and time changes
322 .It Pa /var/log/messages
323 record of the user setting the time
328 utility exits 0 on success, 1 if unable to set the date, and 2
329 if able to set the local date, but unable to set it globally.
333 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
336 .Bd -literal -offset indent
341 In the Europe/London timezone, the command:
343 .Dl "date -v1m -v+1y"
347 .Dl "Sun Jan 4 04:15:24 GMT 1998"
349 where it is currently
350 .Li "Mon Aug 4 04:15:24 BST 1997" .
354 .Dl "date -v1d -v3m -v0y -v-1d"
356 will display the last day of February in the year 2000:
358 .Dl "Tue Feb 29 03:18:00 GMT 2000"
362 .Dl "date -v3m -v30d -v0y -v-1m"
364 because there is no such date as the 30th of February.
368 .Dl "date -v1d -v+1m -v-1d -v-fri"
370 will display the last Friday of the month:
372 .Dl "Fri Aug 29 04:31:11 BST 1997"
374 where it is currently
375 .Li "Mon Aug 4 04:31:11 BST 1997" .
379 .Dl "date 8506131627"
382 .Dq Li "June 13, 1985, 4:27 PM" .
384 .Dl "date ""+%Y%m%d%H%M.%S"""
386 may be used on one machine to print out the date
387 suitable for setting on another.
388 .Qq ( Li "+%m%d%H%M%Y.%S"
398 without modifying the date.
402 .Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
404 can be used to parse the output from
406 and express it in Epoch time.
410 synchronizes the time on many hosts, the setting of a new time value may
411 require more than a few seconds.
415 .Ql Network time being set .
417 .Ql Communication error with timed
418 occurs when the communication
432 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
439 utility is expected to be compatible with
442 .Fl d , f , j , n , r , t ,
445 options are all extensions to the standard.