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 2, 2024 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 , 144.Cm seconds , 145and 146.Cm ns No Pq for nanoseconds . 147The date and time is formatted to the specified precision. 148When 149.Ar FMT 150is 151.Cm hours 152.Po or the more precise 153.Cm minutes , 154.Cm seconds , 155or 156.Cm ns Pc , 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 by a plus or minus sign, 229the date is adjusted forward or backward 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 forward 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 and 331.Ql %N 332for nanoseconds, as well as any arbitrary text. 333A newline 334.Pq Ql \en 335character is always output after the characters specified by 336the format string. 337The format string for the default display is 338.Dq +%+ . 339.Pp 340If an operand does not have a leading plus sign, it is interpreted as 341a value for setting the system's notion of the current date and time. 342The canonical representation for setting the date and time is: 343.Pp 344.Bl -tag -width Ds -compact -offset indent 345.It Ar cc 346Century 347(either 19 or 20) 348prepended to the abbreviated year. 349.It Ar yy 350Year in abbreviated form 351(e.g., 89 for 1989, 06 for 2006). 352.It Ar mm 353Numeric month, a number from 1 to 12. 354.It Ar dd 355Day, a number from 1 to 31. 356.It Ar HH 357Hour, a number from 0 to 23. 358.It Ar MM 359Minutes, a number from 0 to 59. 360.It Ar SS 361Seconds, a number from 0 to 60 362(59 plus a potential leap second). 363.El 364.Pp 365Everything but the minutes is optional. 366.Pp 367.Nm 368understands the time zone definitions from the IANA Time Zone Database, 369.Sy tzdata , 370located in 371.Pa /usr/share/zoneinfo . 372Time changes for Daylight Saving Time, standard time, leap seconds 373and leap years are handled automatically. 374.Pp 375There are two ways to specify the time zone: 376.Pp 377If the file or symlink 378.Pa /etc/localtime 379exists, it is interpreted as a time zone definition file, usually in 380the directory hierarchy 381.Pa /usr/share/zoneinfo , 382which contains the time zone definitions from 383.Sy tzdata . 384.Pp 385If the environment variable 386.Ev TZ 387is set, its value is interpreted as the name of a time zone definition 388file, either an absolute path or a relative path to a time zone 389definition in 390.Pa /usr/share/zoneinfo . 391The 392.Ev TZ 393variable overrides 394.Pa /etc/localtime . 395.Pp 396If the time zone definition file is invalid, 397.Nm 398silently reverts to UTC. 399.Pp 400Previous versions of 401.Nm 402included the 403.Fl d 404(set daylight saving time flag) and 405.Fl t 406(set negative time zone offset) options, but these details are now 407handled automatically by 408.Sy tzdata . 409Modern offsets are positive for time zones ahead of UTC and negative 410for time zones behind UTC, but like the obsolete 411.Fl t 412option, the 413.Sy tzdata 414files in the subdirectory 415.Pa /usr/share/zoneinfo/Etc 416still use an older convention where times ahead of UTC are considered 417negative. 418.Sh ENVIRONMENT 419The following environment variable affects the execution of 420.Nm : 421.Bl -tag -width Ds 422.It Ev TZ 423The timezone to use when displaying dates. 424The normal format is a pathname relative to 425.Pa /usr/share/zoneinfo . 426For example, the command 427.Dq TZ=America/Los_Angeles date 428displays the current time in California. 429The variable can also specify an absolute path. 430See 431.Xr environ 7 432for more information. 433.El 434.Sh FILES 435.Bl -tag -width /var/log/messages -compact 436.It Pa /etc/localtime 437Time zone information file for default system time zone. 438May be omitted, in which case the default time zone is UTC. 439.It Pa /usr/share/zoneinfo 440Directory containing time zone information files. 441.It Pa /var/log/messages 442Record of the user setting the time. 443.It Pa /var/log/utx.log 444Record of date resets and time changes. 445.El 446.Sh EXIT STATUS 447The 448.Nm 449utility exits 0 on success, 1 if unable to set the date, and 2 450if able to set the local date, but unable to set it globally. 451.Sh EXAMPLES 452The command: 453.Pp 454.Dl "date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S""" 455.Pp 456will display: 457.Bd -literal -offset indent 458DATE: 1987-11-21 459TIME: 13:36:16 460.Ed 461.Pp 462In the Europe/London timezone, the command: 463.Pp 464.Dl "date -v1m -v+1y" 465.Pp 466will display: 467.Pp 468.Dl "Sun Jan 4 04:15:24 GMT 1998" 469.Pp 470where it is currently 471.Li "Mon Aug 4 04:15:24 BST 1997" . 472.Pp 473The command: 474.Pp 475.Dl "date -v1d -v3m -v0y -v-1d" 476.Pp 477will display the last day of February in the year 2000: 478.Pp 479.Dl "Tue Feb 29 03:18:00 GMT 2000" 480.Pp 481So will the command: 482.Pp 483.Dl "date -v3m -v30d -v0y -v-1m" 484.Pp 485because there is no such date as the 30th of February. 486.Pp 487The command: 488.Pp 489.Dl "date -v1d -v+1m -v-1d -v-fri" 490.Pp 491will display the last Friday of the month: 492.Pp 493.Dl "Fri Aug 29 04:31:11 BST 1997" 494.Pp 495where it is currently 496.Li "Mon Aug 4 04:31:11 BST 1997" . 497.Pp 498The command: 499.Pp 500.Dl "date 8506131627" 501.Pp 502sets the date to 503.Dq Li "June 13, 1985, 4:27 PM" . 504.Pp 505.Dl "date ""+%Y%m%d%H%M.%S""" 506.Pp 507may be used on one machine to print out the date 508suitable for setting on another. 509.Qq ( Li "+%m%d%H%M%Y.%S" 510for use on 511.Tn Linux . ) 512.Pp 513The command: 514.Pp 515.Dl "date 1432" 516.Pp 517sets the time to 518.Li "2:32 PM" , 519without modifying the date. 520.Pp 521The command 522.Pp 523.Dl "TZ=America/Los_Angeles date -Iseconds -r 1533415339" 524.Pp 525will display 526.Pp 527.Dl "2018-08-04T13:42:19-07:00" 528.Pp 529The command: 530.Pp 531.Dl "env LC_ALL=C date -j -f ""%a %b %d %T %Z %Y"" ""`env LC_ALL=C date`"" ""+%s""" 532.Pp 533can be used to parse the output from 534.Nm 535and express it in Epoch time. 536.Pp 537Finally the command 538.Pp 539.Dl "TZ=America/Los_Angeles date -z Europe/Paris -j 0900" 540.Pp 541will print the time in the "Europe/Paris" timezone when it is 9:00 in The 542America/Los_Angeles timezone. 543.Sh DIAGNOSTICS 544It is invalid to combine the 545.Fl I 546flag with either 547.Fl R 548or an output format 549.Dq ( + Ns ... ) 550operand. 551If this occurs, 552.Nm 553prints: 554.Ql multiple output formats specified 555and exits with status 1. 556.Sh SEE ALSO 557.Xr locale 1 , 558.Xr clock_gettime 2 , 559.Xr gettimeofday 2 , 560.Xr getutxent 3 , 561.Xr strftime 3 , 562.Xr strptime 3 , 563.Xr tzset 3 , 564.Xr adjkerntz 8 , 565.Xr ntpd 8 , 566.Xr tzsetup 8 567.Rs 568.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD" 569.%A R. Gusella 570.%A S. Zatti 571.Re 572.Rs 573.%U https://iana.org/time-zones 574.%T Time Zone Database 575.Re 576.Sh STANDARDS 577The 578.Nm 579utility is expected to be compatible with 580.St -p1003.2 . 581With the exception of the 582.Fl u 583option, all options are extensions to the standard. 584.Pp 585The format selected by the 586.Fl I 587flag is compatible with 588.St -iso8601 . 589.Pp 590The 591.Ql %N 592conversion specification for nanoseconds is a non-standard extension. 593It is compatible with GNU date's 594.Ql %N . 595.Sh HISTORY 596A 597.Nm 598command appeared in 599.At v1 . 600.Pp 601A number of options were added and then removed again, including the 602.Fl d 603(set DST flag) and 604.Fl t 605(set negative time zone offset). 606Time zones are now handled by code bundled with 607.Sy tzdata . 608.Pp 609The 610.Fl I 611flag was added in 612.Fx 12.0 . 613.Pp 614The 615.Ql %N 616conversion specification was added in 617.Fx 14.1 . 618