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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
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:
96 as the format string to parse the
98 provided rather than using the default
109 Parsing is done using
111 .It Fl I Ns Op Ar FMT
116 may be omitted, in which case the default is
126 The date and time is formatted to the specified precision.
137 format includes the timezone.
139 Do not try to set the date.
140 This allows you to use the
142 flag in addition to the
144 option to convert one date format to another.
145 Note that any date or time components unspecified by the
147 format string take their values from the current time.
149 Obsolete flag, accepted and ignored for compatibility.
151 Use RFC 2822 date and time output format.
152 This is equivalent to using
153 .Dq Li %a, %d %b %Y \&%T %z
162 Print the date and time represented by
166 is the number of seconds since the Epoch
167 (00:00:00 UTC, January 1, 1970;
170 and can be specified in decimal, octal, or hex.
172 Print the date and time of the last modification of
175 Display or set the date in
177 (Coordinated Universal) time.
179 Adjust (i.e., take the current date and display the result of the
180 adjustment; not actually set the date) the second, minute, hour, month
181 day, week day, month or year according to
185 is preceded with a plus or minus sign,
186 the date is adjusted forwards or backwards according to the remaining string,
187 otherwise the relevant part of the date is set.
188 The date can be adjusted as many times as required using these flags.
189 Flags are processed in the order given.
192 (rather than adjusting them),
193 seconds are in the range 0-59, minutes are in the range 0-59, hours are
194 in the range 0-23, month days are in the range 1-31, week days are in the
196 months are in the range 1-12 (Jan-Dec)
197 and years are in the range 80-38 or 1980-2038.
201 is numeric, one of either
210 must be used to specify which part of the date is to be adjusted.
212 The week day or month may be specified using a name rather than a
214 If a name is used with the plus
216 sign, the date will be put forwards
220 date that matches the given week day or month.
221 This will not adjust the date,
222 if the given week day or month is the same as the current one.
224 When a date is adjusted to a specific value or in units greater than hours,
225 daylight savings time considerations are ignored.
226 Adjustments in units of hours or less honor daylight saving time.
227 So, assuming the current date is March 26, 0:30 and that the DST adjustment
228 means that the clock goes forward at 01:00 to 02:00, using
230 will adjust the date to March 26, 2:30.
231 Likewise, if the date is October 29, 0:30 and the DST adjustment means that
232 the clock goes back at 02:00 to 01:00, using
234 will be necessary to reach October 29, 2:30.
236 When the date is adjusted to a specific value that does not actually exist
237 (for example March 26, 1:30 BST 2000 in the Europe/London timezone),
238 the date will be silently adjusted forwards in units of one hour until it
239 reaches a valid time.
240 When the date is adjusted to a specific value that occurs twice
241 (for example October 29, 1:30 2000),
242 the resulting timezone will be set so that the date matches the earlier of
245 It is not possible to adjust a date to an invalid absolute day, so using
247 .Fl v No 31d Fl v No 12m
248 will simply fail five months of the year.
249 It is therefore usual to set the month before setting the day; using
250 .Fl v No 12m Fl v No 31d
253 Adjusting the date by months is inherently ambiguous because
254 a month is a unit of variable length depending on the current date.
255 This kind of date adjustment is applied in the most intuitive way.
258 tries to preserve the day of the month.
259 If it is impossible because the target month is shorter than the present one,
260 the last day of the target month will be the result.
263 on May 31 will adjust the date to June 30, while using the same option
264 on January 30 will result in the date adjusted to the last day of February.
265 This approach is also believed to make the most sense for shell scripting.
266 Nevertheless, be aware that going forth and back by the same number of
267 months may take you to a different date.
269 Refer to the examples below for further details.
272 An operand with a leading plus
274 sign signals a user-defined format string
275 which specifies the format in which to display the date and time.
276 The format string may contain any of the conversion specifications
279 manual page, as well as any arbitrary text.
282 character is always output after the characters specified by
284 The format string for the default display is
287 If an operand does not have a leading plus sign, it is interpreted as
288 a value for setting the system's notion of the current date and time.
289 The canonical representation for setting the date and time is:
291 .Bl -tag -width Ds -compact -offset indent
295 prepended to the abbreviated year.
297 Year in abbreviated form
298 (e.g., 89 for 1989, 06 for 2006).
300 Numeric month, a number from 1 to 12.
302 Day, a number from 1 to 31.
304 Hour, a number from 0 to 23.
306 Minutes, a number from 0 to 59.
308 Seconds, a number from 0 to 60
309 (59 plus a potential leap second).
312 Everything but the minutes is optional.
314 Time changes for Daylight Saving Time, standard time, leap seconds,
315 and leap years are handled automatically.
317 The following environment variables affect the execution of
321 The timezone to use when displaying dates.
322 The normal format is a pathname relative to
323 .Pa /usr/share/zoneinfo .
324 For example, the command
325 .Dq TZ=America/Los_Angeles date
326 displays the current time in California.
329 for more information.
332 .Bl -tag -width /var/log/messages -compact
333 .It Pa /var/log/utx.log
334 record of date resets and time changes
335 .It Pa /var/log/messages
336 record of the user setting the time
341 utility exits 0 on success, 1 if unable to set the date, and 2
342 if able to set the local date, but unable to set it globally.
346 .Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
349 .Bd -literal -offset indent
354 In the Europe/London timezone, the command:
356 .Dl "date -v1m -v+1y"
360 .Dl "Sun Jan 4 04:15:24 GMT 1998"
362 where it is currently
363 .Li "Mon Aug 4 04:15:24 BST 1997" .
367 .Dl "date -v1d -v3m -v0y -v-1d"
369 will display the last day of February in the year 2000:
371 .Dl "Tue Feb 29 03:18:00 GMT 2000"
375 .Dl "date -v3m -v30d -v0y -v-1m"
377 because there is no such date as the 30th of February.
381 .Dl "date -v1d -v+1m -v-1d -v-fri"
383 will display the last Friday of the month:
385 .Dl "Fri Aug 29 04:31:11 BST 1997"
387 where it is currently
388 .Li "Mon Aug 4 04:31:11 BST 1997" .
392 .Dl "date 8506131627"
395 .Dq Li "June 13, 1985, 4:27 PM" .
397 .Dl "date ""+%Y%m%d%H%M.%S"""
399 may be used on one machine to print out the date
400 suitable for setting on another.
401 .Qq ( Li "+%m%d%H%M%Y.%S"
411 without modifying the date.
415 .Dl "TZ=America/Los_Angeles date -Iseconds -r 1533415339"
419 .Dl "2018-08-04T13:42:19-07:00"
423 .Dl "date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
425 can be used to parse the output from
427 and express it in Epoch time.
429 It is invalid to combine the
439 .Ql multiple output formats specified
440 and exits with an error status.
448 .%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
455 utility is expected to be compatible with
458 .Fl d , f , I , j , r , t ,
461 options are all extensions to the standard.
463 The format selected by the
465 flag is compatible with