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32 .\" @(#)date.1 8.3 (Berkeley) 4/28/95
39 .Nd display or set date and time
44 .Op Fl z Ar output_zone
52 .Ar val Op Cm y | m | w | d | H | M | S
55 .Op Cm + Ns Ar output_fmt
56 .\" Set time with the default input format.
59 .Op Fl z Ar output_zone
65 .Ar val Op Cm y | m | w | d | H | M | S
75 .Oc Ar MM Op Cm \&. Ar SS
77 .Op Cm + Ns Ar output_fmt
78 .\" Set time with the user-provided input format.
81 .Op Fl z Ar output_zone
87 .Ar val Op Cm y | m | w | d | H | M | S
92 .Op Cm + Ns Ar output_fmt
94 When invoked without arguments, the
96 utility displays the current date and time.
97 Otherwise, depending on the options specified,
99 will set the date and time or print it in a user-defined way.
103 utility displays the date and time read from the kernel clock.
104 When used to set the date and time,
105 both the kernel clock and the hardware clock are updated.
107 Only the superuser may set the date,
108 and if the system securelevel (see
111 the time may not be changed by more than 1 second.
113 The options are as follows:
115 .It Fl f Ar input_fmt
118 as the format string to parse the
120 provided rather than using the default
128 .Oc Ar MM Op Cm \&. Ar SS
131 Parsing is done using
133 .It Fl I Ns Op Ar FMT
138 may be omitted, in which case the default is
148 The date and time is formatted to the specified precision.
159 format includes the timezone.
161 Do not try to set the date.
162 This allows you to use the
164 flag in addition to the
166 option to convert one date format to another.
167 Note that any date or time components unspecified by the
169 format string take their values from the current time.
171 Obsolete flag, accepted and ignored for compatibility.
173 Use RFC 2822 date and time output format.
174 This is equivalent to using
175 .Dq Li %a, %d %b %Y \&%T %z
184 Print the date and time represented by
188 is the number of seconds since the Epoch
189 (00:00:00 UTC, January 1, 1970;
192 and can be specified in decimal, octal, or hex.
194 Print the date and time of the last modification of
197 Display or set the date in
199 (Coordinated Universal) time.
202 displays the time in the time zone described by
206 environment variable.
207 .It Fl z Ar output_zone
208 Just before printing the time, change to the specified timezone;
209 see the description of
212 This can be used with
214 to easily convert time specifications from one zone to another.
219 .Ar val Op Cm y | m | w | d | H | M | S
222 Adjust (i.e., take the current date and display the result of the
223 adjustment; not actually set the date) the second, minute, hour, month
224 day, week day, month or year according to
228 is preceded with a plus or minus sign,
229 the date is adjusted forwards or backwards according to the remaining string,
230 otherwise the relevant part of the date is set.
231 The date can be adjusted as many times as required using these flags.
232 Flags are processed in the order given.
235 (rather than adjusting them),
236 seconds are in the range 0-59, minutes are in the range 0-59, hours are
237 in the range 0-23, month days are in the range 1-31, week days are in the
239 months are in the range 1-12 (Jan-Dec)
240 and years are in a limited range depending on the platform.
242 On i386, years are in the range 69-38 representing 1969-2038.
243 On every other platform, years 0-68 are accepted and represent 2000-2068, and
244 69-99 are accepted and represent 1969-1999.
245 In both cases, years between 100 and 1900 (both included) are accepted and
246 interpreted as relative to 1900 of the Gregorian calendar with a limit of 138 on
247 i386 and a much higher limit on every other platform.
248 Years starting at 1901 are also accepted, and are interpreted as absolute years.
252 is numeric, one of either
261 must be used to specify which part of the date is to be adjusted.
263 The week day or month may be specified using a name rather than a
265 If a name is used with the plus
267 sign, the date will be put forwards
271 date that matches the given week day or month.
272 This will not adjust the date,
273 if the given week day or month is the same as the current one.
275 When a date is adjusted to a specific value or in units greater than hours,
276 daylight savings time considerations are ignored.
277 Adjustments in units of hours or less honor daylight saving time.
278 So, assuming the current date is March 26, 0:30 and that the DST adjustment
279 means that the clock goes forward at 01:00 to 02:00, using
281 will adjust the date to March 26, 2:30.
282 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
283 the clock goes back at 02:00 to 01:00, using
285 will be necessary to reach October 29, 2:30.
287 When the date is adjusted to a specific value that does not actually exist
288 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
289 the date will be silently adjusted forwards in units of one hour until it
290 reaches a valid time.
291 When the date is adjusted to a specific value that occurs twice
292 (for example October 29, 1:30 2000),
293 the resulting timezone will be set so that the date matches the earlier of
296 It is not possible to adjust a date to an invalid absolute day, so using
298 .Fl v No 31d Fl v No 12m
299 will simply fail five months of the year.
300 It is therefore usual to set the month before setting the day; using
301 .Fl v No 12m Fl v No 31d
304 Adjusting the date by months is inherently ambiguous because
305 a month is a unit of variable length depending on the current date.
306 This kind of date adjustment is applied in the most intuitive way.
309 tries to preserve the day of the month.
310 If it is impossible because the target month is shorter than the present one,
311 the last day of the target month will be the result.
314 on May 31 will adjust the date to June 30, while using the same option
315 on January 30 will result in the date adjusted to the last day of February.
316 This approach is also believed to make the most sense for shell scripting.
317 Nevertheless, be aware that going forth and back by the same number of
318 months may take you to a different date.
320 Refer to the examples below for further details.
323 An operand with a leading plus
325 sign signals a user-defined format string
326 which specifies the format in which to display the date and time.
327 The format string may contain any of the conversion specifications
330 manual page, as well as any arbitrary text.
333 character is always output after the characters specified by
335 The format string for the default display is
338 If an operand does not have a leading plus sign, it is interpreted as
339 a value for setting the system's notion of the current date and time.
340 The canonical representation for setting the date and time is:
342 .Bl -tag -width Ds -compact -offset indent
346 prepended to the abbreviated year.
348 Year in abbreviated form
349 (e.g., 89 for 1989, 06 for 2006).
351 Numeric month, a number from 1 to 12.
353 Day, a number from 1 to 31.
355 Hour, a number from 0 to 23.
357 Minutes, a number from 0 to 59.
359 Seconds, a number from 0 to 60
360 (59 plus a potential leap second).
363 Everything but the minutes is optional.
366 understands the time zone definitions from the IANA Time Zone Database,
369 .Pa /usr/share/zoneinfo .
370 Time changes for Daylight Saving Time, standard time, leap seconds
371 and leap years are handled automatically.
373 There are two ways to specify the time zone:
375 If the file or symlink
377 exists, it is interpreted as a time zone definition file, usually in
378 the directory hierarchy
379 .Pa /usr/share/zoneinfo ,
380 which contains the time zone definitions from
383 If the environment variable
385 is set, its value is interpreted as the name of a time zone definition
386 file, either an absolute path or a relative path to a time zone
388 .Pa /usr/share/zoneinfo .
394 If the time zone definition file is invalid,
396 silently reverts to UTC.
402 (set daylight saving time flag) and
404 (set negative time zone offset) options, but these details are now
405 handled automatically by
407 Modern offsets are positive for time zones ahead of UTC and negative
408 for time zones behind UTC, but like the obsolete
412 files in the subdirectory
413 .Pa /usr/share/zoneinfo/Etc
414 still use an older convention where times ahead of UTC are considered
417 The following environment variable affects the execution of
421 The timezone to use when displaying dates.
422 The normal format is a pathname relative to
423 .Pa /usr/share/zoneinfo .
424 For example, the command
425 .Dq TZ=America/Los_Angeles date
426 displays the current time in California.
427 The variable can also specify an absolute path.
430 for more information.
433 .Bl -tag -width /var/log/messages -compact
434 .It Pa /etc/localtime
435 Time zone information file for default system time zone.
436 May be omitted, in which case the default time zone is UTC.
437 .It Pa /usr/share/zoneinfo
438 Directory containing time zone information files.
439 .It Pa /var/log/messages
440 Record of the user setting the time.
441 .It Pa /var/log/utx.log
442 Record of date resets and time changes.
447 utility exits 0 on success, 1 if unable to set the date, and 2
448 if able to set the local date, but unable to set it globally.
452 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
455 .Bd -literal -offset indent
460 In the Europe/London timezone, the command:
462 .Dl "date -v1m -v+1y"
466 .Dl "Sun Jan 4 04:15:24 GMT 1998"
468 where it is currently
469 .Li "Mon Aug 4 04:15:24 BST 1997" .
473 .Dl "date -v1d -v3m -v0y -v-1d"
475 will display the last day of February in the year 2000:
477 .Dl "Tue Feb 29 03:18:00 GMT 2000"
481 .Dl "date -v3m -v30d -v0y -v-1m"
483 because there is no such date as the 30th of February.
487 .Dl "date -v1d -v+1m -v-1d -v-fri"
489 will display the last Friday of the month:
491 .Dl "Fri Aug 29 04:31:11 BST 1997"
493 where it is currently
494 .Li "Mon Aug 4 04:31:11 BST 1997" .
498 .Dl "date 8506131627"
501 .Dq Li "June 13, 1985, 4:27 PM" .
503 .Dl "date ""+%Y%m%d%H%M.%S"""
505 may be used on one machine to print out the date
506 suitable for setting on another.
507 .Qq ( Li "+%m%d%H%M%Y.%S"
517 without modifying the date.
521 .Dl "TZ=America/Los_Angeles date -Iseconds -r 1533415339"
525 .Dl "2018-08-04T13:42:19-07:00"
529 .Dl "env LC_ALL=C date -j -f ""%a %b %d %T %Z %Y"" ""`env LC_ALL=C date`"" ""+%s"""
531 can be used to parse the output from
533 and express it in Epoch time.
537 .Dl "TZ=America/Los_Angeles date -z Europe/Paris -j 0900"
539 will print the time in the "Europe/Paris" timezone when it is 9:00 in The
540 America/Los_Angeles timezone.
542 It is invalid to combine the
552 .Ql multiple output formats specified
553 and exits with status 1.
565 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
570 .%U https://iana.org/time-zones
571 .%T Time Zone Database
576 utility is expected to be compatible with
578 With the exception of the
580 option, all options are extensions to the standard.
582 The format selected by the
584 flag is compatible with
592 A number of options were added and then removed again, including the
596 (set negative time zone offset).
597 Time zones are now handled by code bundled with