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.\" @(#)date.1 8.3 (Berkeley) 4/28/95 33.\" 34.Dd May 19, 2023 35.Dt DATE 1 36.Os 37.Sh NAME 38.Nm date 39.Nd display or set date and time 40.Sh SYNOPSIS 41.\" Display time. 42.Nm 43.Op Fl nRu 44.Op Fl z Ar output_zone 45.Op Fl I Ns Op Ar FMT 46.Op Fl r Ar filename 47.Op Fl r Ar seconds 48.Oo 49.Sm off 50.Fl v 51.Op Cm + | - 52.Ar val Op Cm y | m | w | d | H | M | S 53.Sm on 54.Oc 55.Op Cm + Ns Ar output_fmt 56.\" Set time with the default input format. 57.Nm 58.Op Fl jnRu 59.Op Fl z Ar output_zone 60.Op Fl I Ns Op Ar FMT 61.Oo 62.Sm off 63.Fl v 64.Op Cm + | - 65.Ar val Op Cm y | m | w | d | H | M | S 66.Sm on 67.Oc 68.Sm off 69.Oo Oo Oo Oo Oo 70.Ar cc Oc 71.Ar yy Oc 72.Ar mm Oc 73.Ar dd Oc 74.Ar HH 75.Oc Ar MM Op Cm \&. Ar SS 76.Sm on 77.Op Cm + Ns Ar output_fmt 78.\" Set time with the user-provided input format. 79.Nm 80.Op Fl jnRu 81.Op Fl z Ar output_zone 82.Op Fl I Ns Op Ar FMT 83.Oo 84.Sm off 85.Fl v 86.Op Cm + | - 87.Ar val Op Cm y | m | w | d | H | M | S 88.Sm on 89.Oc 90.Fl f Ar input_fmt 91.Ar new_date 92.Op Cm + Ns Ar output_fmt 93.Sh DESCRIPTION 94When invoked without arguments, the 95.Nm 96utility displays the current date and time. 97Otherwise, depending on the options specified, 98.Nm 99will set the date and time or print it in a user-defined way. 100.Pp 101The 102.Nm 103utility displays the date and time read from the kernel clock. 104When used to set the date and time, 105both the kernel clock and the hardware clock are updated. 106.Pp 107Only the superuser may set the date, 108and if the system securelevel (see 109.Xr securelevel 7 ) 110is greater than 1, 111the time may not be changed by more than 1 second. 112.Pp 113The options are as follows: 114.Bl -tag -width Ds 115.It Fl f Ar input_fmt 116Use 117.Ar input_fmt 118as the format string to parse the 119.Ar new_date 120provided rather than using the default 121.Sm off 122.Oo Oo Oo Oo Oo 123.Ar cc Oc 124.Ar yy Oc 125.Ar mm Oc 126.Ar dd Oc 127.Ar HH 128.Oc Ar MM Op Cm \&. Ar SS 129.Sm on 130format. 131Parsing is done using 132.Xr strptime 3 . 133.It Fl I Ns Op Ar FMT 134Use 135.St -iso8601 136output format. 137.Ar FMT 138may be omitted, in which case the default is 139.Cm date . 140Valid 141.Ar FMT 142values are 143.Cm date , 144.Cm hours , 145.Cm minutes , 146and 147.Cm seconds . 148The date and time is formatted to the specified precision. 149When 150.Ar FMT 151is 152.Cm hours 153(or the more precise 154.Cm minutes 155or 156.Cm seconds ) , 157the 158.St -iso8601 159format includes the timezone. 160.It Fl j 161Do not try to set the date. 162This allows you to use the 163.Fl f 164flag in addition to the 165.Cm + 166option to convert one date format to another. 167Note that any date or time components unspecified by the 168.Fl f 169format string take their values from the current time. 170.It Fl n 171Obsolete flag, accepted and ignored for compatibility. 172.It Fl R 173Use RFC 2822 date and time output format. 174This is equivalent to using 175.Dq Li %a, %d %b %Y \&%T %z 176as 177.Ar output_fmt 178while 179.Ev LC_TIME 180is set to the 181.Dq C 182locale . 183.It Fl r Ar seconds 184Print the date and time represented by 185.Ar seconds , 186where 187.Ar seconds 188is the number of seconds since the Epoch 189(00:00:00 UTC, January 1, 1970; 190see 191.Xr time 3 ) , 192and can be specified in decimal, octal, or hex. 193.It Fl r Ar filename 194Print the date and time of the last modification of 195.Ar filename . 196.It Fl u 197Display or set the date in 198.Tn UTC 199(Coordinated Universal) time. 200By default 201.Nm 202displays the time in the time zone described by 203.Pa /etc/localtime 204or the 205.Ev TZ 206environment variable. 207.It Fl z Ar output_zone 208Just before printing the time, change to the specified timezone; 209see the description of 210.Ev TZ 211below. 212This can be used with 213.Fl j 214to easily convert time specifications from one zone to another. 215.It Xo 216.Fl v 217.Sm off 218.Op Cm + | - 219.Ar val Op Cm y | m | w | d | H | M | S 220.Sm on 221.Xc 222Adjust (i.e., take the current date and display the result of the 223adjustment; not actually set the date) the second, minute, hour, month 224day, week day, month or year according to 225.Ar val . 226If 227.Ar val 228is preceded with a plus or minus sign, 229the date is adjusted forwards or backwards according to the remaining string, 230otherwise the relevant part of the date is set. 231The date can be adjusted as many times as required using these flags. 232Flags are processed in the order given. 233.Pp 234When setting values 235(rather than adjusting them), 236seconds are in the range 0-59, minutes are in the range 0-59, hours are 237in the range 0-23, month days are in the range 1-31, week days are in the 238range 0-6 (Sun-Sat), 239months are in the range 1-12 (Jan-Dec) 240and years are in a limited range depending on the platform. 241.Pp 242On i386, years are in the range 69-38 representing 1969-2038. 243On every other platform, years 0-68 are accepted and represent 2000-2068, and 24469-99 are accepted and represent 1969-1999. 245In both cases, years between 100 and 1900 (both included) are accepted and 246interpreted as relative to 1900 of the Gregorian calendar with a limit of 138 on 247i386 and a much higher limit on every other platform. 248Years starting at 1901 are also accepted, and are interpreted as absolute years. 249.Pp 250If 251.Ar val 252is numeric, one of either 253.Cm y , 254.Cm m , 255.Cm w , 256.Cm d , 257.Cm H , 258.Cm M 259or 260.Cm S 261must be used to specify which part of the date is to be adjusted. 262.Pp 263The week day or month may be specified using a name rather than a 264number. 265If a name is used with the plus 266(or minus) 267sign, the date will be put forwards 268(or backwards) 269to the next 270(previous) 271date that matches the given week day or month. 272This will not adjust the date, 273if the given week day or month is the same as the current one. 274.Pp 275When a date is adjusted to a specific value or in units greater than hours, 276daylight savings time considerations are ignored. 277Adjustments in units of hours or less honor daylight saving time. 278So, assuming the current date is March 26, 0:30 and that the DST adjustment 279means that the clock goes forward at 01:00 to 02:00, using 280.Fl v No +1H 281will adjust the date to March 26, 2:30. 282Likewise, if the date is October 29, 0:30 and the DST adjustment means that 283the clock goes back at 02:00 to 01:00, using 284.Fl v No +3H 285will be necessary to reach October 29, 2:30. 286.Pp 287When 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), 289the date will be silently adjusted forwards in units of one hour until it 290reaches a valid time. 291When the date is adjusted to a specific value that occurs twice 292(for example October 29, 1:30 2000), 293the resulting timezone will be set so that the date matches the earlier of 294the two times. 295.Pp 296It is not possible to adjust a date to an invalid absolute day, so using 297the switches 298.Fl v No 31d Fl v No 12m 299will simply fail five months of the year. 300It is therefore usual to set the month before setting the day; using 301.Fl v No 12m Fl v No 31d 302always works. 303.Pp 304Adjusting the date by months is inherently ambiguous because 305a month is a unit of variable length depending on the current date. 306This kind of date adjustment is applied in the most intuitive way. 307First of all, 308.Nm 309tries to preserve the day of the month. 310If it is impossible because the target month is shorter than the present one, 311the last day of the target month will be the result. 312For example, using 313.Fl v No +1m 314on May 31 will adjust the date to June 30, while using the same option 315on January 30 will result in the date adjusted to the last day of February. 316This approach is also believed to make the most sense for shell scripting. 317Nevertheless, be aware that going forth and back by the same number of 318months may take you to a different date. 319.Pp 320Refer to the examples below for further details. 321.El 322.Pp 323An operand with a leading plus 324.Pq Sq + 325sign signals a user-defined format string 326which specifies the format in which to display the date and time. 327The format string may contain any of the conversion specifications 328described in the 329.Xr strftime 3 330manual page, as well as any arbitrary text. 331A newline 332.Pq Ql \en 333character is always output after the characters specified by 334the format string. 335The format string for the default display is 336.Dq +%+ . 337.Pp 338If an operand does not have a leading plus sign, it is interpreted as 339a value for setting the system's notion of the current date and time. 340The canonical representation for setting the date and time is: 341.Pp 342.Bl -tag -width Ds -compact -offset indent 343.It Ar cc 344Century 345(either 19 or 20) 346prepended to the abbreviated year. 347.It Ar yy 348Year in abbreviated form 349(e.g., 89 for 1989, 06 for 2006). 350.It Ar mm 351Numeric month, a number from 1 to 12. 352.It Ar dd 353Day, a number from 1 to 31. 354.It Ar HH 355Hour, a number from 0 to 23. 356.It Ar MM 357Minutes, a number from 0 to 59. 358.It Ar SS 359Seconds, a number from 0 to 60 360(59 plus a potential leap second). 361.El 362.Pp 363Everything but the minutes is optional. 364.Pp 365.Nm 366understands the time zone definitions from the IANA Time Zone Database, 367.Sy tzdata , 368located in 369.Pa /usr/share/zoneinfo . 370Time changes for Daylight Saving Time, standard time, leap seconds 371and leap years are handled automatically. 372.Pp 373There are two ways to specify the time zone: 374.Pp 375If the file or symlink 376.Pa /etc/localtime 377exists, it is interpreted as a time zone definition file, usually in 378the directory hierarchy 379.Pa /usr/share/zoneinfo , 380which contains the time zone definitions from 381.Sy tzdata . 382.Pp 383If the environment variable 384.Ev TZ 385is set, its value is interpreted as the name of a time zone definition 386file, either an absolute path or a relative path to a time zone 387definition in 388.Pa /usr/share/zoneinfo . 389The 390.Ev TZ 391variable overrides 392.Pa /etc/localtime . 393.Pp 394If the time zone definition file is invalid, 395.Nm 396silently reverts to UTC. 397.Pp 398Previous versions of 399.Nm 400included the 401.Fl d 402(set daylight saving time flag) and 403.Fl t 404(set negative time zone offset) options, but these details are now 405handled automatically by 406.Sy tzdata . 407Modern offsets are positive for time zones ahead of UTC and negative 408for time zones behind UTC, but like the obsolete 409.Fl t 410option, the 411.Sy tzdata 412files in the subdirectory 413.Pa /usr/share/zoneinfo/Etc 414still use an older convention where times ahead of UTC are considered 415negative. 416.Sh ENVIRONMENT 417The following environment variable affects the execution of 418.Nm : 419.Bl -tag -width Ds 420.It Ev TZ 421The timezone to use when displaying dates. 422The normal format is a pathname relative to 423.Pa /usr/share/zoneinfo . 424For example, the command 425.Dq TZ=America/Los_Angeles date 426displays the current time in California. 427The variable can also specify an absolute path. 428See 429.Xr environ 7 430for more information. 431.El 432.Sh FILES 433.Bl -tag -width /var/log/messages -compact 434.It Pa /etc/localtime 435Time zone information file for default system time zone. 436May be omitted, in which case the default time zone is UTC. 437.It Pa /usr/share/zoneinfo 438Directory containing time zone information files. 439.It Pa /var/log/messages 440Record of the user setting the time. 441.It Pa /var/log/utx.log 442Record of date resets and time changes. 443.El 444.Sh EXIT STATUS 445The 446.Nm 447utility exits 0 on success, 1 if unable to set the date, and 2 448if able to set the local date, but unable to set it globally. 449.Sh EXAMPLES 450The command: 451.Pp 452.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S""" 453.Pp 454will display: 455.Bd -literal -offset indent 456DATE: 1987-11-21 457TIME: 13:36:16 458.Ed 459.Pp 460In the Europe/London timezone, the command: 461.Pp 462.Dl "date -v1m -v+1y" 463.Pp 464will display: 465.Pp 466.Dl "Sun Jan 4 04:15:24 GMT 1998" 467.Pp 468where it is currently 469.Li "Mon Aug 4 04:15:24 BST 1997" . 470.Pp 471The command: 472.Pp 473.Dl "date -v1d -v3m -v0y -v-1d" 474.Pp 475will display the last day of February in the year 2000: 476.Pp 477.Dl "Tue Feb 29 03:18:00 GMT 2000" 478.Pp 479So will the command: 480.Pp 481.Dl "date -v3m -v30d -v0y -v-1m" 482.Pp 483because there is no such date as the 30th of February. 484.Pp 485The command: 486.Pp 487.Dl "date -v1d -v+1m -v-1d -v-fri" 488.Pp 489will display the last Friday of the month: 490.Pp 491.Dl "Fri Aug 29 04:31:11 BST 1997" 492.Pp 493where it is currently 494.Li "Mon Aug 4 04:31:11 BST 1997" . 495.Pp 496The command: 497.Pp 498.Dl "date 8506131627" 499.Pp 500sets the date to 501.Dq Li "June 13, 1985, 4:27 PM" . 502.Pp 503.Dl "date ""+%Y%m%d%H%M.%S""" 504.Pp 505may be used on one machine to print out the date 506suitable for setting on another. 507.Qq ( Li "+%m%d%H%M%Y.%S" 508for use on 509.Tn Linux . ) 510.Pp 511The command: 512.Pp 513.Dl "date 1432" 514.Pp 515sets the time to 516.Li "2:32 PM" , 517without modifying the date. 518.Pp 519The command 520.Pp 521.Dl "TZ=America/Los_Angeles date -Iseconds -r 1533415339" 522.Pp 523will display 524.Pp 525.Dl "2018-08-04T13:42:19-07:00" 526.Pp 527The command: 528.Pp 529.Dl "env LC_ALL=C date -j -f ""%a %b %d %T %Z %Y"" ""`env LC_ALL=C date`"" ""+%s""" 530.Pp 531can be used to parse the output from 532.Nm 533and express it in Epoch time. 534.Pp 535Finally the command 536.Pp 537.Dl "TZ=America/Los_Angeles date -z Europe/Paris -j 0900" 538.Pp 539will print the time in the "Europe/Paris" timezone when it is 9:00 in The 540America/Los_Angeles timezone. 541.Sh DIAGNOSTICS 542It is invalid to combine the 543.Fl I 544flag with either 545.Fl R 546or an output format 547.Dq ( + Ns ... ) 548operand. 549If this occurs, 550.Nm 551prints: 552.Ql multiple output formats specified 553and exits with status 1. 554.Sh SEE ALSO 555.Xr locale 1 , 556.Xr gettimeofday 2 , 557.Xr getutxent 3 , 558.Xr strftime 3 , 559.Xr strptime 3 , 560.Xr tzset 3 , 561.Xr adjkerntz 8 , 562.Xr ntpd 8 , 563.Xr tzsetup 8 564.Rs 565.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" 566.%A R. Gusella 567.%A S. Zatti 568.Re 569.Rs 570.%U https://iana.org/time-zones 571.%T Time Zone Database 572.Re 573.Sh STANDARDS 574The 575.Nm 576utility is expected to be compatible with 577.St -p1003.2 . 578With the exception of the 579.Fl u 580option, all options are extensions to the standard. 581.Pp 582The format selected by the 583.Fl I 584flag is compatible with 585.St -iso8601 . 586.Sh HISTORY 587A 588.Nm 589command appeared in 590.At v1 . 591.Pp 592A number of options were added and then removed again, including the 593.Fl d 594(set DST flag) and 595.Fl t 596(set negative time zone offset). 597Time zones are now handled by code bundled with 598.Sy tzdata . 599.Pp 600The 601.Fl I 602flag was added in 603.Fx 12.0 . 604