1.\"- 2.\" Copyright (c) 1980, 1990, 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" This code is derived from software contributed to Berkeley by 6.\" the Institute of Electrical and Electronics Engineers, Inc. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.Dd May 19, 2023 33.Dt DATE 1 34.Os 35.Sh NAME 36.Nm date 37.Nd display or set date and time 38.Sh SYNOPSIS 39.\" Display time. 40.Nm 41.Op Fl nRu 42.Op Fl z Ar output_zone 43.Op Fl I Ns Op Ar FMT 44.Op Fl r Ar filename 45.Op Fl r Ar seconds 46.Oo 47.Sm off 48.Fl v 49.Op Cm + | - 50.Ar val Op Cm y | m | w | d | H | M | S 51.Sm on 52.Oc 53.Op Cm + Ns Ar output_fmt 54.\" Set time with the default input format. 55.Nm 56.Op Fl jnRu 57.Op Fl z Ar output_zone 58.Op Fl I Ns Op Ar FMT 59.Oo 60.Sm off 61.Fl v 62.Op Cm + | - 63.Ar val Op Cm y | m | w | d | H | M | S 64.Sm on 65.Oc 66.Sm off 67.Oo Oo Oo Oo Oo 68.Ar cc Oc 69.Ar yy Oc 70.Ar mm Oc 71.Ar dd Oc 72.Ar HH 73.Oc Ar MM Op Cm \&. Ar SS 74.Sm on 75.Op Cm + Ns Ar output_fmt 76.\" Set time with the user-provided input format. 77.Nm 78.Op Fl jnRu 79.Op Fl z Ar output_zone 80.Op Fl I Ns Op Ar FMT 81.Oo 82.Sm off 83.Fl v 84.Op Cm + | - 85.Ar val Op Cm y | m | w | d | H | M | S 86.Sm on 87.Oc 88.Fl f Ar input_fmt 89.Ar new_date 90.Op Cm + Ns Ar output_fmt 91.Sh DESCRIPTION 92When invoked without arguments, the 93.Nm 94utility displays the current date and time. 95Otherwise, depending on the options specified, 96.Nm 97will set the date and time or print it in a user-defined way. 98.Pp 99The 100.Nm 101utility displays the date and time read from the kernel clock. 102When used to set the date and time, 103both the kernel clock and the hardware clock are updated. 104.Pp 105Only the superuser may set the date, 106and if the system securelevel (see 107.Xr securelevel 7 ) 108is greater than 1, 109the time may not be changed by more than 1 second. 110.Pp 111The options are as follows: 112.Bl -tag -width Ds 113.It Fl f Ar input_fmt 114Use 115.Ar input_fmt 116as the format string to parse the 117.Ar new_date 118provided rather than using the default 119.Sm off 120.Oo Oo Oo Oo Oo 121.Ar cc Oc 122.Ar yy Oc 123.Ar mm Oc 124.Ar dd Oc 125.Ar HH 126.Oc Ar MM Op Cm \&. Ar SS 127.Sm on 128format. 129Parsing is done using 130.Xr strptime 3 . 131.It Fl I Ns Op Ar FMT 132Use 133.St -iso8601 134output format. 135.Ar FMT 136may be omitted, in which case the default is 137.Cm date . 138Valid 139.Ar FMT 140values are 141.Cm date , 142.Cm hours , 143.Cm minutes , 144and 145.Cm seconds . 146The date and time is formatted to the specified precision. 147When 148.Ar FMT 149is 150.Cm hours 151(or the more precise 152.Cm minutes 153or 154.Cm seconds ) , 155the 156.St -iso8601 157format includes the timezone. 158.It Fl j 159Do not try to set the date. 160This allows you to use the 161.Fl f 162flag in addition to the 163.Cm + 164option to convert one date format to another. 165Note that any date or time components unspecified by the 166.Fl f 167format string take their values from the current time. 168.It Fl n 169Obsolete flag, accepted and ignored for compatibility. 170.It Fl R 171Use RFC 2822 date and time output format. 172This is equivalent to using 173.Dq Li %a, %d %b %Y \&%T %z 174as 175.Ar output_fmt 176while 177.Ev LC_TIME 178is set to the 179.Dq C 180locale . 181.It Fl r Ar seconds 182Print the date and time represented by 183.Ar seconds , 184where 185.Ar seconds 186is the number of seconds since the Epoch 187(00:00:00 UTC, January 1, 1970; 188see 189.Xr time 3 ) , 190and can be specified in decimal, octal, or hex. 191.It Fl r Ar filename 192Print the date and time of the last modification of 193.Ar filename . 194.It Fl u 195Display or set the date in 196.Tn UTC 197(Coordinated Universal) time. 198By default 199.Nm 200displays the time in the time zone described by 201.Pa /etc/localtime 202or the 203.Ev TZ 204environment variable. 205.It Fl z Ar output_zone 206Just before printing the time, change to the specified timezone; 207see the description of 208.Ev TZ 209below. 210This can be used with 211.Fl j 212to easily convert time specifications from one zone to another. 213.It Xo 214.Fl v 215.Sm off 216.Op Cm + | - 217.Ar val Op Cm y | m | w | d | H | M | S 218.Sm on 219.Xc 220Adjust (i.e., take the current date and display the result of the 221adjustment; not actually set the date) the second, minute, hour, month 222day, week day, month or year according to 223.Ar val . 224If 225.Ar val 226is preceded by a plus or minus sign, 227the date is adjusted forward or backward according to the remaining string, 228otherwise the relevant part of the date is set. 229The date can be adjusted as many times as required using these flags. 230Flags are processed in the order given. 231.Pp 232When setting values 233(rather than adjusting them), 234seconds are in the range 0-59, minutes are in the range 0-59, hours are 235in the range 0-23, month days are in the range 1-31, week days are in the 236range 0-6 (Sun-Sat), 237months are in the range 1-12 (Jan-Dec) 238and years are in a limited range depending on the platform. 239.Pp 240On i386, years are in the range 69-38 representing 1969-2038. 241On every other platform, years 0-68 are accepted and represent 2000-2068, and 24269-99 are accepted and represent 1969-1999. 243In both cases, years between 100 and 1900 (both included) are accepted and 244interpreted as relative to 1900 of the Gregorian calendar with a limit of 138 on 245i386 and a much higher limit on every other platform. 246Years starting at 1901 are also accepted, and are interpreted as absolute years. 247.Pp 248If 249.Ar val 250is numeric, one of either 251.Cm y , 252.Cm m , 253.Cm w , 254.Cm d , 255.Cm H , 256.Cm M 257or 258.Cm S 259must be used to specify which part of the date is to be adjusted. 260.Pp 261The week day or month may be specified using a name rather than a 262number. 263If a name is used with the plus 264(or minus) 265sign, the date will be put forwards 266(or backwards) 267to the next 268(previous) 269date that matches the given week day or month. 270This will not adjust the date, 271if the given week day or month is the same as the current one. 272.Pp 273When a date is adjusted to a specific value or in units greater than hours, 274daylight savings time considerations are ignored. 275Adjustments in units of hours or less honor daylight saving time. 276So, assuming the current date is March 26, 0:30 and that the DST adjustment 277means that the clock goes forward at 01:00 to 02:00, using 278.Fl v No +1H 279will adjust the date to March 26, 2:30. 280Likewise, if the date is October 29, 0:30 and the DST adjustment means that 281the clock goes back at 02:00 to 01:00, using 282.Fl v No +3H 283will be necessary to reach October 29, 2:30. 284.Pp 285When the date is adjusted to a specific value that does not actually exist 286(for example March 26, 1:30 BST 2000 in the Europe/London timezone), 287the date will be silently adjusted forward in units of one hour until it 288reaches a valid time. 289When the date is adjusted to a specific value that occurs twice 290(for example October 29, 1:30 2000), 291the resulting timezone will be set so that the date matches the earlier of 292the two times. 293.Pp 294It is not possible to adjust a date to an invalid absolute day, so using 295the switches 296.Fl v No 31d Fl v No 12m 297will simply fail five months of the year. 298It is therefore usual to set the month before setting the day; using 299.Fl v No 12m Fl v No 31d 300always works. 301.Pp 302Adjusting the date by months is inherently ambiguous because 303a month is a unit of variable length depending on the current date. 304This kind of date adjustment is applied in the most intuitive way. 305First of all, 306.Nm 307tries to preserve the day of the month. 308If it is impossible because the target month is shorter than the present one, 309the last day of the target month will be the result. 310For example, using 311.Fl v No +1m 312on May 31 will adjust the date to June 30, while using the same option 313on January 30 will result in the date adjusted to the last day of February. 314This approach is also believed to make the most sense for shell scripting. 315Nevertheless, be aware that going forth and back by the same number of 316months may take you to a different date. 317.Pp 318Refer to the examples below for further details. 319.El 320.Pp 321An operand with a leading plus 322.Pq Sq + 323sign signals a user-defined format string 324which specifies the format in which to display the date and time. 325The format string may contain any of the conversion specifications 326described in the 327.Xr strftime 3 328manual page, as well as any arbitrary text. 329A newline 330.Pq Ql \en 331character is always output after the characters specified by 332the format string. 333The format string for the default display is 334.Dq +%+ . 335.Pp 336If an operand does not have a leading plus sign, it is interpreted as 337a value for setting the system's notion of the current date and time. 338The canonical representation for setting the date and time is: 339.Pp 340.Bl -tag -width Ds -compact -offset indent 341.It Ar cc 342Century 343(either 19 or 20) 344prepended to the abbreviated year. 345.It Ar yy 346Year in abbreviated form 347(e.g., 89 for 1989, 06 for 2006). 348.It Ar mm 349Numeric month, a number from 1 to 12. 350.It Ar dd 351Day, a number from 1 to 31. 352.It Ar HH 353Hour, a number from 0 to 23. 354.It Ar MM 355Minutes, a number from 0 to 59. 356.It Ar SS 357Seconds, a number from 0 to 60 358(59 plus a potential leap second). 359.El 360.Pp 361Everything but the minutes is optional. 362.Pp 363.Nm 364understands the time zone definitions from the IANA Time Zone Database, 365.Sy tzdata , 366located in 367.Pa /usr/share/zoneinfo . 368Time changes for Daylight Saving Time, standard time, leap seconds 369and leap years are handled automatically. 370.Pp 371There are two ways to specify the time zone: 372.Pp 373If the file or symlink 374.Pa /etc/localtime 375exists, it is interpreted as a time zone definition file, usually in 376the directory hierarchy 377.Pa /usr/share/zoneinfo , 378which contains the time zone definitions from 379.Sy tzdata . 380.Pp 381If the environment variable 382.Ev TZ 383is set, its value is interpreted as the name of a time zone definition 384file, either an absolute path or a relative path to a time zone 385definition in 386.Pa /usr/share/zoneinfo . 387The 388.Ev TZ 389variable overrides 390.Pa /etc/localtime . 391.Pp 392If the time zone definition file is invalid, 393.Nm 394silently reverts to UTC. 395.Pp 396Previous versions of 397.Nm 398included the 399.Fl d 400(set daylight saving time flag) and 401.Fl t 402(set negative time zone offset) options, but these details are now 403handled automatically by 404.Sy tzdata . 405Modern offsets are positive for time zones ahead of UTC and negative 406for time zones behind UTC, but like the obsolete 407.Fl t 408option, the 409.Sy tzdata 410files in the subdirectory 411.Pa /usr/share/zoneinfo/Etc 412still use an older convention where times ahead of UTC are considered 413negative. 414.Sh ENVIRONMENT 415The following environment variable affects the execution of 416.Nm : 417.Bl -tag -width Ds 418.It Ev TZ 419The timezone to use when displaying dates. 420The normal format is a pathname relative to 421.Pa /usr/share/zoneinfo . 422For example, the command 423.Dq TZ=America/Los_Angeles date 424displays the current time in California. 425The variable can also specify an absolute path. 426See 427.Xr environ 7 428for more information. 429.El 430.Sh FILES 431.Bl -tag -width /var/log/messages -compact 432.It Pa /etc/localtime 433Time zone information file for default system time zone. 434May be omitted, in which case the default time zone is UTC. 435.It Pa /usr/share/zoneinfo 436Directory containing time zone information files. 437.It Pa /var/log/messages 438Record of the user setting the time. 439.It Pa /var/log/utx.log 440Record of date resets and time changes. 441.El 442.Sh EXIT STATUS 443The 444.Nm 445utility exits 0 on success, 1 if unable to set the date, and 2 446if able to set the local date, but unable to set it globally. 447.Sh EXAMPLES 448The command: 449.Pp 450.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S""" 451.Pp 452will display: 453.Bd -literal -offset indent 454DATE: 1987-11-21 455TIME: 13:36:16 456.Ed 457.Pp 458In the Europe/London timezone, the command: 459.Pp 460.Dl "date -v1m -v+1y" 461.Pp 462will display: 463.Pp 464.Dl "Sun Jan 4 04:15:24 GMT 1998" 465.Pp 466where it is currently 467.Li "Mon Aug 4 04:15:24 BST 1997" . 468.Pp 469The command: 470.Pp 471.Dl "date -v1d -v3m -v0y -v-1d" 472.Pp 473will display the last day of February in the year 2000: 474.Pp 475.Dl "Tue Feb 29 03:18:00 GMT 2000" 476.Pp 477So will the command: 478.Pp 479.Dl "date -v3m -v30d -v0y -v-1m" 480.Pp 481because there is no such date as the 30th of February. 482.Pp 483The command: 484.Pp 485.Dl "date -v1d -v+1m -v-1d -v-fri" 486.Pp 487will display the last Friday of the month: 488.Pp 489.Dl "Fri Aug 29 04:31:11 BST 1997" 490.Pp 491where it is currently 492.Li "Mon Aug 4 04:31:11 BST 1997" . 493.Pp 494The command: 495.Pp 496.Dl "date 8506131627" 497.Pp 498sets the date to 499.Dq Li "June 13, 1985, 4:27 PM" . 500.Pp 501.Dl "date ""+%Y%m%d%H%M.%S""" 502.Pp 503may be used on one machine to print out the date 504suitable for setting on another. 505.Qq ( Li "+%m%d%H%M%Y.%S" 506for use on 507.Tn Linux . ) 508.Pp 509The command: 510.Pp 511.Dl "date 1432" 512.Pp 513sets the time to 514.Li "2:32 PM" , 515without modifying the date. 516.Pp 517The command 518.Pp 519.Dl "TZ=America/Los_Angeles date -Iseconds -r 1533415339" 520.Pp 521will display 522.Pp 523.Dl "2018-08-04T13:42:19-07:00" 524.Pp 525The command: 526.Pp 527.Dl "env LC_ALL=C date -j -f ""%a %b %d %T %Z %Y"" ""`env LC_ALL=C date`"" ""+%s""" 528.Pp 529can be used to parse the output from 530.Nm 531and express it in Epoch time. 532.Pp 533Finally the command 534.Pp 535.Dl "TZ=America/Los_Angeles date -z Europe/Paris -j 0900" 536.Pp 537will print the time in the "Europe/Paris" timezone when it is 9:00 in The 538America/Los_Angeles timezone. 539.Sh DIAGNOSTICS 540It is invalid to combine the 541.Fl I 542flag with either 543.Fl R 544or an output format 545.Dq ( + Ns ... ) 546operand. 547If this occurs, 548.Nm 549prints: 550.Ql multiple output formats specified 551and exits with status 1. 552.Sh SEE ALSO 553.Xr locale 1 , 554.Xr gettimeofday 2 , 555.Xr getutxent 3 , 556.Xr strftime 3 , 557.Xr strptime 3 , 558.Xr tzset 3 , 559.Xr adjkerntz 8 , 560.Xr ntpd 8 , 561.Xr tzsetup 8 562.Rs 563.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" 564.%A R. Gusella 565.%A S. Zatti 566.Re 567.Rs 568.%U https://iana.org/time-zones 569.%T Time Zone Database 570.Re 571.Sh STANDARDS 572The 573.Nm 574utility is expected to be compatible with 575.St -p1003.2 . 576With the exception of the 577.Fl u 578option, all options are extensions to the standard. 579.Pp 580The format selected by the 581.Fl I 582flag is compatible with 583.St -iso8601 . 584.Sh HISTORY 585A 586.Nm 587command appeared in 588.At v1 . 589.Pp 590A number of options were added and then removed again, including the 591.Fl d 592(set DST flag) and 593.Fl t 594(set negative time zone offset). 595Time zones are now handled by code bundled with 596.Sy tzdata . 597.Pp 598The 599.Fl I 600flag was added in 601.Fx 12.0 . 602