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32 .\" @(#)date.1 8.3 (Berkeley) 4/28/95
40 .Nd display or set date and time
44 .Op Fl r Ar seconds | Ar filename
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.
135 This is equivalent to using
136 .Dq Li %a, %d %b %Y \&%T %z
145 Print the date and time represented by
149 is the number of seconds since the Epoch
150 (00:00:00 UTC, January 1, 1970;
153 and can be specified in decimal, octal, or hex.
155 Print the date and time of the last modification of
157 .It Fl t Ar minutes_west
158 Set the system's value for minutes west of
161 specifies the number of minutes returned in
166 Display or set the date in
168 (Coordinated Universal) time.
170 Adjust (i.e., take the current date and display the result of the
171 adjustment; not actually set the date) the second, minute, hour, month
172 day, week day, month or year according to
176 is preceded with a plus or minus sign,
177 the date is adjusted forwards or backwards according to the remaining string,
178 otherwise the relevant part of the date is set.
179 The date can be adjusted as many times as required using these flags.
180 Flags are processed in the order given.
183 (rather than adjusting them),
184 seconds are in the range 0-59, minutes are in the range 0-59, hours are
185 in the range 0-23, month days are in the range 1-31, week days are in the
187 months are in the range 1-12 (Jan-Dec)
188 and years are in the range 80-38 or 1980-2038.
192 is numeric, one of either
201 must be used to specify which part of the date is to be adjusted.
203 The week day or month may be specified using a name rather than a
205 If a name is used with the plus
207 sign, the date will be put forwards
211 date that matches the given week day or month.
212 This will not adjust the date,
213 if the given week day or month is the same as the current one.
215 When a date is adjusted to a specific value or in units greater than hours,
216 daylight savings time considerations are ignored.
217 Adjustments in units of hours or less honor daylight saving time.
218 So, assuming the current date is March 26, 0:30 and that the DST adjustment
219 means that the clock goes forward at 01:00 to 02:00, using
221 will adjust the date to March 26, 2:30.
222 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
223 the clock goes back at 02:00 to 01:00, using
225 will be necessary to reach October 29, 2:30.
227 When the date is adjusted to a specific value that does not actually exist
228 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
229 the date will be silently adjusted forwards in units of one hour until it
230 reaches a valid time.
231 When the date is adjusted to a specific value that occurs twice
232 (for example October 29, 1:30 2000),
233 the resulting timezone will be set so that the date matches the earlier of
236 It is not possible to adjust a date to an invalid absolute day, so using
238 .Fl v No 31d Fl v No 12m
239 will simply fail five months of the year.
240 It is therefore usual to set the month before setting the day; using
241 .Fl v No 12m Fl v No 31d
244 Adjusting the date by months is inherently ambiguous because
245 a month is a unit of variable length depending on the current date.
246 This kind of date adjustment is applied in the most intuitive way.
249 tries to preserve the day of the month.
250 If it is impossible because the target month is shorter than the present one,
251 the last day of the target month will be the result.
254 on May 31 will adjust the date to June 30, while using the same option
255 on January 30 will result in the date adjusted to the last day of February.
256 This approach is also believed to make the most sense for shell scripting.
257 Nevertheless, be aware that going forth and back by the same number of
258 months may take you to a different date.
260 Refer to the examples below for further details.
263 An operand with a leading plus
265 sign signals a user-defined format string
266 which specifies the format in which to display the date and time.
267 The format string may contain any of the conversion specifications
270 manual page, as well as any arbitrary text.
273 character is always output after the characters specified by
275 The format string for the default display is
278 If an operand does not have a leading plus sign, it is interpreted as
279 a value for setting the system's notion of the current date and time.
280 The canonical representation for setting the date and time is:
282 .Bl -tag -width Ds -compact -offset indent
286 prepended to the abbreviated year.
288 Year in abbreviated form
289 (e.g., 89 for 1989, 06 for 2006).
291 Numeric month, a number from 1 to 12.
293 Day, a number from 1 to 31.
295 Hour, a number from 0 to 23.
297 Minutes, a number from 0 to 59.
299 Seconds, a number from 0 to 61
300 (59 plus a maximum of two leap seconds).
303 Everything but the minutes is optional.
305 Time changes for Daylight Saving Time, standard time, leap seconds,
306 and leap years are handled automatically.
308 The following environment variables affect the execution of
312 The timezone to use when displaying dates.
313 The normal format is a pathname relative to
314 .Pa /usr/share/zoneinfo .
315 For example, the command
316 .Dq TZ=America/Los_Angeles date
317 displays the current time in California.
320 for more information.
323 .Bl -tag -width /var/log/messages -compact
324 .It Pa /var/log/utx.log
325 record of date resets and time changes
326 .It Pa /var/log/messages
327 record of the user setting the time
332 utility exits 0 on success, 1 if unable to set the date, and 2
333 if able to set the local date, but unable to set it globally.
337 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
340 .Bd -literal -offset indent
345 In the Europe/London timezone, the command:
347 .Dl "date -v1m -v+1y"
351 .Dl "Sun Jan 4 04:15:24 GMT 1998"
353 where it is currently
354 .Li "Mon Aug 4 04:15:24 BST 1997" .
358 .Dl "date -v1d -v3m -v0y -v-1d"
360 will display the last day of February in the year 2000:
362 .Dl "Tue Feb 29 03:18:00 GMT 2000"
366 .Dl "date -v3m -v30d -v0y -v-1m"
368 because there is no such date as the 30th of February.
372 .Dl "date -v1d -v+1m -v-1d -v-fri"
374 will display the last Friday of the month:
376 .Dl "Fri Aug 29 04:31:11 BST 1997"
378 where it is currently
379 .Li "Mon Aug 4 04:31:11 BST 1997" .
383 .Dl "date 8506131627"
386 .Dq Li "June 13, 1985, 4:27 PM" .
388 .Dl "date ""+%Y%m%d%H%M.%S"""
390 may be used on one machine to print out the date
391 suitable for setting on another.
392 .Qq ( Li "+%m%d%H%M%Y.%S"
402 without modifying the date.
406 .Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
408 can be used to parse the output from
410 and express it in Epoch time.
414 synchronizes the time on many hosts, the setting of a new time value may
415 require more than a few seconds.
419 .Ql Network time being set .
421 .Ql Communication error with timed
422 occurs when the communication
436 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
443 utility is expected to be compatible with
446 .Fl d , f , j , n , r , t ,
449 options are all extensions to the standard.