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35 .\" @(#)date.1 8.3 (Berkeley) 4/28/95
36 .\" $FreeBSD: src/bin/date/date.1,v 1.34.2.15 2003/02/24 03:01:00 trhodes Exp $
37 .\" $DragonFly: src/bin/date/date.1,v 1.3 2005/07/20 06:10:51 cpressey Exp $
44 .Nd display or set date and time
50 .Op Fl t Ar minutes_west
63 .Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH
69 When invoked without arguments, the
71 utility displays the current date and time.
72 Otherwise, depending on the options specified,
74 will set the date and time or print it in a user-defined way.
78 utility displays the date and time read from the kernel clock.
79 When used to set the date and time,
80 both the kernel clock and the hardware clock are updated.
82 Only the superuser may set the date,
83 and if the system securelevel (see
86 the time may not be changed by more than 1 second.
88 The options are as follows:
91 Set the kernel's value for daylight saving time.
94 is non-zero, future calls
97 will return a non-zero for
102 as the format string to parse the
104 provided rather than using the default
115 Parsing is done using
118 Do not try to set the date.
119 This allows you to use the
121 flag in addition to the
123 option to convert one date format to another.
129 sets the time on all of the machines in the local group.
132 option suppresses this behavior and causes the time to be set only on the
135 Print the date and time represented by
139 is the number of seconds since the Epoch
140 (00:00:00 UTC, January 1, 1970;
143 and can be specified in decimal, octal, or hex.
144 .It Fl t Ar minutes_west
145 Set the system's value for minutes west of
148 specifies the number of minutes returned in
153 Display or set the date in
155 (Coordinated Universal) time.
157 Adjust (i.e., take the current date and display the result of the
158 adjustment; not actually set the date) the second, minute, hour, month
159 day, week day, month or year according to
163 is preceded with a plus or minus sign,
164 the date is adjusted forwards or backwards according to the remaining string,
165 otherwise the relevant part of the date is set.
166 The date can be adjusted as many times as required using these flags.
167 Flags are processed in the order given.
170 (rather than adjusting them),
171 seconds are in the range 0-59, minutes are in the range 0-59, hours are
172 in the range 0-23, month days are in the range 1-31, week days are in the
174 months are in the range 1-12 (Jan-Dec)
175 and years are in the range 80-38 or 1980-2038.
179 is numeric, one of either
188 must be used to specify which part of the date is to be adjusted.
190 The week day or month may be specified using a name rather than a
192 If a name is used with the plus
194 sign, the date will be put forwards
198 date that matches the given week day or month.
199 This will not adjust the date,
200 if the given week day or month is the same as the current one.
202 When a date is adjusted to a specific value or in units greater than hours,
203 daylight savings time considerations are ignored.
204 Adjustments in units of hours or less honor daylight saving time.
205 So, assuming the current date is March 26, 0:30 and that the DST adjustment
206 means that the clock goes forward at 01:00 to 02:00, using
208 will adjust the date to March 26, 2:30.
209 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
210 the clock goes back at 02:00 to 01:00, using
212 will be necessary to reach October 29, 2:30.
214 When the date is adjusted to a specific value that doesn't actually exist
215 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
216 the date will be silently adjusted forwards in units of one hour until it
217 reaches a valid time.
218 When the date is adjusted to a specific value that occurs twice
219 (for example October 29, 1:30 2000),
220 the resulting timezone will be set so that the date matches the earlier of
223 Adjusting the date by months is inherently ambiguous because
224 a month is a unit of variable length depending on the current date.
225 This kind of date adjustment is applied in the most intuitive way.
228 tries to preserve the day of the month.
229 If it is impossible because the target month is shorter than the present one,
230 the last day of the target month will be the result.
233 on May 31 will adjust the date to June 30, while using the same option
234 on January 30 will result in the date adjusted to the last day of February.
235 This approach is also believed to make the most sense for shell scripting.
236 Nevertheless, be aware that going forth and back by the same number of
237 months may take you to a different date.
239 Refer to the examples below for further details.
242 An operand with a leading plus
244 sign signals a user-defined format string
245 which specifies the format in which to display the date and time.
246 The format string may contain any of the conversion specifications
249 manual page, as well as any arbitrary text.
252 character is always output after the characters specified by
254 The format string for the default display is
257 If an operand does not have a leading plus sign, it is interpreted as
258 a value for setting the system's notion of the current date and time.
259 The canonical representation for setting the date and time is:
261 .Bl -tag -width Ds -compact -offset indent
265 prepended to the abbreviated year.
267 Year in abbreviated form
268 (e.g. 89 for 1989, 06 for 2006).
270 Numeric month, a number from 1 to 12.
272 Day, a number from 1 to 31.
274 Hour, a number from 0 to 23.
276 Minutes, a number from 0 to 59.
278 Seconds, a number from 0 to 61
279 (59 plus a maximum of two leap seconds).
282 Everything but the minutes is optional.
284 Time changes for Daylight Saving Time, standard time, leap seconds,
285 and leap years are handled automatically.
289 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
292 .Bd -literal -offset indent
297 In the Europe/London timezone, the command:
299 .Dl "date -v1m -v+1y"
303 .Dl "Sun Jan 4 04:15:24 GMT 1998"
305 where it is currently Mon Aug 4 04:15:24 BST 1997.
309 .Dl "date -v1d -v3m -v0y -v-1d"
311 will display the last day of February in the year 2000:
313 .Dl "Tue Feb 29 03:18:00 GMT 2000"
315 So will do the command:
317 .Dl "date -v30d -v3m -v0y -v-1m"
319 because there is no such date as the 30th of February.
323 .Dl "date -v1d -v+1m -v-1d -v-fri"
325 will display the last Friday of the month:
327 .Dl "Fri Aug 29 04:31:11 BST 1997"
329 where it is currently Mon Aug 4 04:31:11 BST 1997.
333 .Dl "date 8506131627"
336 .Dq Li "June 13, 1985, 4:27 PM" .
338 .Dl "date ""+%Y%m%d%H%M.%S"""
340 may be used on one machine to print out the date
341 suitable for setting on another.
349 without modifying the date.
351 The following environment variables affect the execution of
355 The timezone to use when displaying dates.
356 The normal format is a pathname relative to
357 .Pa /usr/share/zoneinfo .
358 For example, the command
359 .Dq TZ=America/Los_Angeles date
360 displays the current time in California.
363 for more information.
366 .Bl -tag -width /var/log/messages -compact
368 record of date resets and time changes
369 .It Pa /var/log/messages
370 record of the user setting the time
379 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
386 utility exits 0 on success, 1 if unable to set the date, and 2
387 if able to set the local date, but unable to set it globally.
391 synchronizes the time on many hosts, the setting of a new time value may
392 require more than a few seconds.
396 .Ql Network time being set .
398 .Ql Communication error with timed
399 occurs when the communication
408 utility is expected to be compatible with