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1.0'
?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.2//EN"
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6 SPDX-License-Identifier: LGPL-2.1+
8 This file is part of systemd.
10 Copyright 2010 Lennart Poettering
12 systemd is free software; you can redistribute it and/or modify it
13 under the terms of the GNU Lesser General Public License as published by
14 the Free Software Foundation; either version 2.1 of the License, or
15 (at your option) any later version.
17 systemd is distributed in the hope that it will be useful, but
18 WITHOUT ANY WARRANTY; without even the implied warranty of
19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 Lesser General Public License for more details.
22 You should have received a copy of the GNU Lesser General Public License
23 along with systemd; If not, see <http://www.gnu.org/licenses/>.
26 <refentry id=
"systemd.time">
29 <title>systemd.time
</title>
30 <productname>systemd
</productname>
34 <contrib>Developer
</contrib>
35 <firstname>Lennart
</firstname>
36 <surname>Poettering
</surname>
37 <email>lennart@poettering.net
</email>
43 <refentrytitle>systemd.time
</refentrytitle>
44 <manvolnum>7</manvolnum>
48 <refname>systemd.time
</refname>
49 <refpurpose>Time and date specifications
</refpurpose>
53 <title>Description
</title>
55 <para>In systemd, timestamps, time spans, and calendar events are
56 displayed and may be specified in closely related syntaxes.
</para>
60 <title>Displaying Time Spans
</title>
62 <para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
63 of time values each suffixed by a time unit. Example:
</para>
65 <programlisting>2h
30min
</programlisting>
67 <para>All specified time values are meant to be added up. The above hence refers to
150 minutes. Display is
68 locale-independent, only English names for the time units are used.
</para>
72 <title>Parsing Time Spans
</title>
74 <para>When parsing, systemd will accept the same time span syntax.
75 Separating spaces may be omitted. The following time units are
79 <listitem><para>usec, us
</para></listitem>
80 <listitem><para>msec, ms
</para></listitem>
81 <listitem><para>seconds, second, sec, s
</para></listitem>
82 <listitem><para>minutes, minute, min, m
</para></listitem>
83 <listitem><para>hours, hour, hr, h
</para></listitem>
84 <listitem><para>days, day, d
</para></listitem>
85 <listitem><para>weeks, week, w
</para></listitem>
86 <listitem><para>months, month, M (defined as
30.44 days)
</para></listitem>
87 <listitem><para>years, year, y (defined as
365.25 days)
</para></listitem>
90 <para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
91 such. In a few cases
<literal>ns
</literal>,
<literal>nsec
</literal> is accepted too, where the granularity of the
92 time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
95 <para>Examples for valid time span specifications:
</para>
102 300ms20s
5day
</programlisting>
106 <title>Displaying Timestamps
</title>
108 <para>Timestamps refer to specific, unique points in time. On
109 display, systemd will format these in the local timezone as
112 <programlisting>Fri
2012-
11-
23 23:
02:
15 CET
</programlisting>
114 <para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.
</para>
116 <para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
117 the
<literal>UTC
</literal> timezone specifier in the output.
</para>
119 <para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
120 separated by a full stop from the seconds component.
</para>
124 <title>Parsing Timestamps
</title>
126 <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
127 as the literal string
<literal>UTC
</literal> (for the UTC timezone), or is specified to be the locally configured
128 timezone, or the timezone name in the IANA timezone database format. The complete list of timezones
129 supported on your system can be obtained using the
<literal>timedatectl list-timezones
</literal>
130 (see
<citerefentry><refentrytitle>timedatectl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
131 Using IANA format is recommended over local timezone names, as less prone to errors (eg: with local timezone it's possible to
132 specify daylight saving time in winter, while it's incorrect). The weekday specification is optional, but when
133 the weekday is specified, it must either be in the abbreviated (
<literal>Wed
</literal>) or non-abbreviated
134 (
<literal>Wednesday
</literal>) English language form (case does not matter), and is not subject to the locale
135 choice of the user. Either the date, or the time part may be omitted, in which case the current date or
00:
00:
00,
136 respectively, is assumed. The seconds component of the time may also be omitted, in which case
":00" is
137 assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).
</para>
139 <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
142 <para>When parsing, systemd will also accept a few special
143 placeholders instead of timestamps:
<literal>now
</literal> may be
144 used to refer to the current time (or of the invocation of the
145 command that is currently executed).
<literal>today
</literal>,
146 <literal>yesterday
</literal>, and
<literal>tomorrow
</literal> refer to
147 00:
00:
00 of the current day, the day before, or the next day,
150 <para>When parsing, systemd will also accept relative time
151 specifications. A time span (see above) that is prefixed with
152 <literal>+
</literal> is evaluated to the current time plus the
153 specified time span. Correspondingly, a time span that is prefixed
154 with
<literal>-
</literal> is evaluated to the current time minus
155 the specified time span. Instead of prefixing the time span with
156 <literal>+
</literal> or
<literal>-
</literal>, it may also be
157 suffixed with a space and the word
<literal>left
</literal> or
158 <literal>ago
</literal>.
</para>
160 <para>Finally, a timespan prefixed with
<literal>@
</literal> is
161 evaluated relative to the UNIX time epoch
1st Jan,
1970,
164 <para>Examples for valid timestamps and their normalized form
165 (assuming the current time was
2012-
11-
23 18:
15:
22 and the timezone
166 was UTC+
8, for example TZ=Asia/Shanghai):
</para>
168 <programlisting> Fri
2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
169 2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
170 2012-
11-
23 11:
12:
13 UTC → Fri
2012-
11-
23 19:
12:
13
171 2012-
11-
23 → Fri
2012-
11-
23 00:
00:
00
172 12-
11-
23 → Fri
2012-
11-
23 00:
00:
00
173 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
174 11:
12 → Fri
2012-
11-
23 11:
12:
00
175 now → Fri
2012-
11-
23 18:
15:
22
176 today → Fri
2012-
11-
23 00:
00:
00
177 today UTC → Fri
2012-
11-
23 16:
00:
00
178 yesterday → Fri
2012-
11-
22 00:
00:
00
179 tomorrow → Fri
2012-
11-
24 00:
00:
00
180 tomorrow Pacific/Auckland → Thu
2012-
11-
23 19:
00:
00
181 +
3h30min → Fri
2012-
11-
23 21:
45:
22
182 -
5s → Fri
2012-
11-
23 18:
15:
17
183 11min ago → Fri
2012-
11-
23 18:
04:
22
184 @
1395716396 → Tue
2014-
03-
25 03:
59:
56</programlisting>
186 <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
187 locally, as the timezone component is not understood (unless it happens to be
<literal>UTC
</literal>).
</para>
189 <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
190 by a full stop from the seconds component. Example:
</para>
192 <programlisting>2014-
03-
25 03:
59:
56.654563</programlisting>
194 <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
195 invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
196 timestamp is formatted as follows:
</para>
198 <programlisting>2 months
5 days ago
</programlisting>
200 <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).
</para>
204 <title>Calendar Events
</title>
206 <para>Calendar events may be used to refer to one or more points
207 in time in a single expression. They form a superset of the
208 absolute timestamps explained above:
</para>
210 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
212 <para>The above refers to
11:
12:
13 of the first or fifth day of
213 any month of the year
2012, but only if that day is a Thursday or
216 <para>The weekday specification is optional. If specified, it
217 should consist of one or more English language weekday names,
218 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
219 form (case does not matter), separated by commas. Specifying two
220 weekdays separated by
<literal>..
</literal> refers to a range of
221 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
222 may be combined freely.
</para>
224 <para>In the date and time specifications, any component may be
225 specified as
<literal>*
</literal> in which case any value will
226 match. Alternatively, each component can be specified as a list of
227 values separated by commas. Values may be suffixed with
228 <literal>/
</literal> and a repetition value, which indicates that
229 the value itself and the value plus all multiples of the repetition value
230 are matched. Two values separated by
<literal>..
</literal> may be used
231 to indicate a range of values; ranges may also be followed with
232 <literal>/
</literal> and a repetition value.
</para>
234 <para>A date specification may use
<literal>~
</literal> to indicate the
235 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
236 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
237 means
"the last Monday in May."</para>
239 <para>The seconds component may contain decimal fractions both in
240 the value and the repetition. All fractions are rounded to
6
241 decimal places.
</para>
243 <para>Either time or date specification may be omitted, in which
244 case the current day and
00:
00:
00 is implied, respectively. If the
245 second component is not specified,
<literal>:
00</literal> is
248 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
249 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
250 in the IANA timezone database format (also see above).
</para>
252 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
254 <programlisting> minutely → *-*-* *:*:
00
255 hourly → *-*-* *:
00:
00
256 daily → *-*-*
00:
00:
00
257 monthly → *-*-
01 00:
00:
00
258 weekly → Mon *-*-*
00:
00:
00
259 yearly → *-
01-
01 00:
00:
00
260 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
261 semiannually → *-
01,
07-
01 00:
00:
00
264 <para>Examples for valid timestamps and their
265 normalized form:
</para>
267 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
268 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
269 Wed *-
1 → Wed *-*-
01 00:
00:
00
270 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
271 Wed,
17:
48 → Wed *-*-*
17:
48:
00
272 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
273 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
274 10-
15 → *-
10-
15 00:
00:
00
275 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
276 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
277 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
278 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
279 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
280 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
281 08:
05:
40 → *-*-*
08:
05:
40
282 05:
40 → *-*-*
05:
40:
00
283 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
284 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
285 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
286 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
287 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
288 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
289 2003-
03-
05 →
2003-
03-
05 00:
00:
00
290 03-
05 → *-
03-
05 00:
00:
00
291 hourly → *-*-* *:
00:
00
292 daily → *-*-*
00:
00:
00
293 daily UTC → *-*-*
00:
00:
00 UTC
294 monthly → *-*-
01 00:
00:
00
295 weekly → Mon *-*-*
00:
00:
00
296 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
297 yearly → *-
01-
01 00:
00:
00
298 annually → *-
01-
01 00:
00:
00
299 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
301 <para>Calendar events are used by timer units, see
302 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
305 <para>Use the
<command>calendar
</command> command of
306 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
307 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
308 calendar event would elapse next.
</para>
312 <title>See Also
</title>
314 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
315 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
316 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
317 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
318 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
319 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>