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35 .\" @(#)date.1 8.3 (Berkeley) 4/28/95
36 .\" $FreeBSD: src/bin/date/date.1,v 1.72 2005/02/13 22:25:09 ru Exp $
37 .\" $DragonFly: src/bin/date/date.1,v 1.4 2005/07/20 20:05:46 cpressey Exp $
44 .Nd display or set date and time
57 .Op Cm + Ns Ar output_fmt
61 .Op Oo Oo Oo Oo Ar cc Oc Ar yy Oc Ar mm Oc Ar dd Oc Ar HH
66 .Fl f Ar input_fmt new_date
67 .Op Cm + Ns Ar output_fmt
70 .Op Fl t Ar minutes_west
72 When invoked without arguments, the
74 utility displays the current date and time.
75 Otherwise, depending on the options specified,
77 will set the date and time or print it in a user-defined way.
81 utility displays the date and time read from the kernel clock.
82 When used to set the date and time,
83 both the kernel clock and the hardware clock are updated.
85 Only the superuser may set the date,
86 and if the system securelevel (see
89 the time may not be changed by more than 1 second.
91 The options are as follows:
94 Set the kernel's value for daylight saving time.
97 is non-zero, future calls
100 will return a non-zero for
105 as the format string to parse the
107 provided rather than using the default
118 Parsing is done using
121 Do not try to set the date.
122 This allows you to use the
124 flag in addition to the
126 option to convert one date format to another.
132 sets the time on all of the machines in the local group.
135 option suppresses this behavior and causes the time to be set only on the
138 Print the date and time represented by
142 is the number of seconds since the Epoch
143 (00:00:00 UTC, January 1, 1970;
146 and can be specified in decimal, octal, or hex.
147 .It Fl t Ar minutes_west
148 Set the system's value for minutes west of
151 specifies the number of minutes returned in
156 Display or set the date in
158 (Coordinated Universal) time.
160 Adjust (i.e., take the current date and display the result of the
161 adjustment; not actually set the date) the second, minute, hour, month
162 day, week day, month or year according to
166 is preceded with a plus or minus sign,
167 the date is adjusted forwards or backwards according to the remaining string,
168 otherwise the relevant part of the date is set.
169 The date can be adjusted as many times as required using these flags.
170 Flags are processed in the order given.
173 (rather than adjusting them),
174 seconds are in the range 0-59, minutes are in the range 0-59, hours are
175 in the range 0-23, month days are in the range 1-31, week days are in the
177 months are in the range 1-12 (Jan-Dec)
178 and years are in the range 80-38 or 1980-2038.
182 is numeric, one of either
191 must be used to specify which part of the date is to be adjusted.
193 The week day or month may be specified using a name rather than a
195 If a name is used with the plus
197 sign, the date will be put forwards
201 date that matches the given week day or month.
202 This will not adjust the date,
203 if the given week day or month is the same as the current one.
205 When a date is adjusted to a specific value or in units greater than hours,
206 daylight savings time considerations are ignored.
207 Adjustments in units of hours or less honor daylight saving time.
208 So, assuming the current date is March 26, 0:30 and that the DST adjustment
209 means that the clock goes forward at 01:00 to 02:00, using
211 will adjust the date to March 26, 2:30.
212 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
213 the clock goes back at 02:00 to 01:00, using
215 will be necessary to reach October 29, 2:30.
217 When the date is adjusted to a specific value that does not actually exist
218 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
219 the date will be silently adjusted forwards in units of one hour until it
220 reaches a valid time.
221 When the date is adjusted to a specific value that occurs twice
222 (for example October 29, 1:30 2000),
223 the resulting timezone will be set so that the date matches the earlier of
226 Adjusting the date by months is inherently ambiguous because
227 a month is a unit of variable length depending on the current date.
228 This kind of date adjustment is applied in the most intuitive way.
231 tries to preserve the day of the month.
232 If it is impossible because the target month is shorter than the present one,
233 the last day of the target month will be the result.
236 on May 31 will adjust the date to June 30, while using the same option
237 on January 30 will result in the date adjusted to the last day of February.
238 This approach is also believed to make the most sense for shell scripting.
239 Nevertheless, be aware that going forth and back by the same number of
240 months may take you to a different date.
242 Refer to the examples below for further details.
245 An operand with a leading plus
247 sign signals a user-defined format string
248 which specifies the format in which to display the date and time.
249 The format string may contain any of the conversion specifications
252 manual page, as well as any arbitrary text.
255 character is always output after the characters specified by
257 The format string for the default display is
260 If an operand does not have a leading plus sign, it is interpreted as
261 a value for setting the system's notion of the current date and time.
262 The canonical representation for setting the date and time is:
264 .Bl -tag -width Ds -compact -offset indent
268 prepended to the abbreviated year.
270 Year in abbreviated form
271 (e.g., 89 for 1989, 06 for 2006).
273 Numeric month, a number from 1 to 12.
275 Day, a number from 1 to 31.
277 Hour, a number from 0 to 23.
279 Minutes, a number from 0 to 59.
281 Seconds, a number from 0 to 61
282 (59 plus a maximum of two leap seconds).
285 Everything but the minutes is optional.
287 Time changes for Daylight Saving Time, standard time, leap seconds,
288 and leap years are handled automatically.
290 The following environment variables affect the execution of
294 The timezone to use when displaying dates.
295 The normal format is a pathname relative to
296 .Pa /usr/share/zoneinfo .
297 For example, the command
298 .Dq TZ=America/Los_Angeles date
299 displays the current time in California.
302 for more information.
305 .Bl -tag -width /var/log/messages -compact
307 record of date resets and time changes
308 .It Pa /var/log/messages
309 record of the user setting the time
314 utility exits 0 on success, 1 if unable to set the date, and 2
315 if able to set the local date, but unable to set it globally.
319 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
322 .Bd -literal -offset indent
327 In the Europe/London timezone, the command:
329 .Dl "date -v1m -v+1y"
333 .Dl "Sun Jan 4 04:15:24 GMT 1998"
335 where it is currently
336 .Li "Mon Aug 4 04:15:24 BST 1997" .
340 .Dl "date -v1d -v3m -v0y -v-1d"
342 will display the last day of February in the year 2000:
344 .Dl "Tue Feb 29 03:18:00 GMT 2000"
346 So will do the command:
348 .Dl "date -v30d -v3m -v0y -v-1m"
350 because there is no such date as the 30th of February.
354 .Dl "date -v1d -v+1m -v-1d -v-fri"
356 will display the last Friday of the month:
358 .Dl "Fri Aug 29 04:31:11 BST 1997"
360 where it is currently
361 .Li "Mon Aug 4 04:31:11 BST 1997" .
365 .Dl "date 8506131627"
368 .Dq Li "June 13, 1985, 4:27 PM" .
370 .Dl "date ""+%Y%m%d%H%M.%S"""
372 may be used on one machine to print out the date
373 suitable for setting on another.
374 .Qq ( Li "+%m%d%H%M%Y.%S"
384 without modifying the date.
388 .Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
390 can be used to parse the output from
392 and express it in Epoch time.
396 synchronizes the time on many hosts, the setting of a new time value may
397 require more than a few seconds.
401 .Ql Network time being set .
403 .Ql Communication error with timed
404 occurs when the communication
417 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
424 utility is expected to be compatible with