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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. 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.
154 Print the date and time of the last modification of
156 .It Fl t Ar minutes_west
157 Set the system's value for minutes west of
160 specifies the number of minutes returned in
165 Display or set the date in
167 (Coordinated Universal) time.
169 Adjust (i.e., take the current date and display the result of the
170 adjustment; not actually set the date) the second, minute, hour, month
171 day, week day, month or year according to
175 is preceded with a plus or minus sign,
176 the date is adjusted forwards or backwards according to the remaining string,
177 otherwise the relevant part of the date is set.
178 The date can be adjusted as many times as required using these flags.
179 Flags are processed in the order given.
182 (rather than adjusting them),
183 seconds are in the range 0-59, minutes are in the range 0-59, hours are
184 in the range 0-23, month days are in the range 1-31, week days are in the
186 months are in the range 1-12 (Jan-Dec)
187 and years are in the range 80-38 or 1980-2038.
191 is numeric, one of either
200 must be used to specify which part of the date is to be adjusted.
202 The week day or month may be specified using a name rather than a
204 If a name is used with the plus
206 sign, the date will be put forwards
210 date that matches the given week day or month.
211 This will not adjust the date,
212 if the given week day or month is the same as the current one.
214 When a date is adjusted to a specific value or in units greater than hours,
215 daylight savings time considerations are ignored.
216 Adjustments in units of hours or less honor daylight saving time.
217 So, assuming the current date is March 26, 0:30 and that the DST adjustment
218 means that the clock goes forward at 01:00 to 02:00, using
220 will adjust the date to March 26, 2:30.
221 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
222 the clock goes back at 02:00 to 01:00, using
224 will be necessary to reach October 29, 2:30.
226 When the date is adjusted to a specific value that does not actually exist
227 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
228 the date will be silently adjusted forwards in units of one hour until it
229 reaches a valid time.
230 When the date is adjusted to a specific value that occurs twice
231 (for example October 29, 1:30 2000),
232 the resulting timezone will be set so that the date matches the earlier of
235 It is not possible to adjust a date to an invalid absolute day, so using
237 .Fl v No 31d Fl v No 12m
238 will simply fail five months of the year.
239 It is therefore usual to set the month before setting the day; using
240 .Fl v No 12m Fl v No 31d
243 Adjusting the date by months is inherently ambiguous because
244 a month is a unit of variable length depending on the current date.
245 This kind of date adjustment is applied in the most intuitive way.
248 tries to preserve the day of the month.
249 If it is impossible because the target month is shorter than the present one,
250 the last day of the target month will be the result.
253 on May 31 will adjust the date to June 30, while using the same option
254 on January 30 will result in the date adjusted to the last day of February.
255 This approach is also believed to make the most sense for shell scripting.
256 Nevertheless, be aware that going forth and back by the same number of
257 months may take you to a different date.
259 Refer to the examples below for further details.
262 An operand with a leading plus
264 sign signals a user-defined format string
265 which specifies the format in which to display the date and time.
266 The format string may contain any of the conversion specifications
269 manual page, as well as any arbitrary text.
272 character is always output after the characters specified by
274 The format string for the default display is
277 If an operand does not have a leading plus sign, it is interpreted as
278 a value for setting the system's notion of the current date and time.
279 The canonical representation for setting the date and time is:
281 .Bl -tag -width Ds -compact -offset indent
285 prepended to the abbreviated year.
287 Year in abbreviated form
288 (e.g., 89 for 1989, 06 for 2006).
290 Numeric month, a number from 1 to 12.
292 Day, a number from 1 to 31.
294 Hour, a number from 0 to 23.
296 Minutes, a number from 0 to 59.
298 Seconds, a number from 0 to 61
299 (59 plus a maximum of two leap seconds).
302 Everything but the minutes is optional.
304 Time changes for Daylight Saving Time, standard time, leap seconds,
305 and leap years are handled automatically.
307 The following environment variables affect the execution of
311 The timezone to use when displaying dates.
312 The normal format is a pathname relative to
313 .Pa /usr/share/zoneinfo .
314 For example, the command
315 .Dq TZ=America/Los_Angeles date
316 displays the current time in California.
319 for more information.
322 .Bl -tag -width /var/log/messages -compact
323 .It Pa /var/log/utx.log
324 record of date resets and time changes
325 .It Pa /var/log/messages
326 record of the user setting the time
331 utility exits 0 on success, 1 if unable to set the date, and 2
332 if able to set the local date, but unable to set it globally.
336 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
339 .Bd -literal -offset indent
344 In the Europe/London timezone, the command:
346 .Dl "date -v1m -v+1y"
350 .Dl "Sun Jan 4 04:15:24 GMT 1998"
352 where it is currently
353 .Li "Mon Aug 4 04:15:24 BST 1997" .
357 .Dl "date -v1d -v3m -v0y -v-1d"
359 will display the last day of February in the year 2000:
361 .Dl "Tue Feb 29 03:18:00 GMT 2000"
365 .Dl "date -v3m -v30d -v0y -v-1m"
367 because there is no such date as the 30th of February.
371 .Dl "date -v1d -v+1m -v-1d -v-fri"
373 will display the last Friday of the month:
375 .Dl "Fri Aug 29 04:31:11 BST 1997"
377 where it is currently
378 .Li "Mon Aug 4 04:31:11 BST 1997" .
382 .Dl "date 8506131627"
385 .Dq Li "June 13, 1985, 4:27 PM" .
387 .Dl "date ""+%Y%m%d%H%M.%S"""
389 may be used on one machine to print out the date
390 suitable for setting on another.
391 .Qq ( Li "+%m%d%H%M%Y.%S"
401 without modifying the date.
405 .Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
407 can be used to parse the output from
409 and express it in Epoch time.
413 synchronizes the time on many hosts, the setting of a new time value may
414 require more than a few seconds.
418 .Ql Network time being set .
420 .Ql Communication error with timed
421 occurs when the communication
435 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
442 utility is expected to be compatible with
445 .Fl d , f , j , n , r , t ,
448 options are all extensions to the standard.