1 <?xml version='
1.0'
?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 SPDX-License-Identifier: LGPL-2.1+
8 This file is part of systemd.
10 Copyright 2010 Lennart Poettering
13 <refentry id=
"systemd.time">
16 <title>systemd.time
</title>
17 <productname>systemd
</productname>
21 <contrib>Developer
</contrib>
22 <firstname>Lennart
</firstname>
23 <surname>Poettering
</surname>
24 <email>lennart@poettering.net
</email>
30 <refentrytitle>systemd.time
</refentrytitle>
31 <manvolnum>7</manvolnum>
35 <refname>systemd.time
</refname>
36 <refpurpose>Time and date specifications
</refpurpose>
40 <title>Description
</title>
42 <para>In systemd, timestamps, time spans, and calendar events are
43 displayed and may be specified in closely related syntaxes.
</para>
47 <title>Displaying Time Spans
</title>
49 <para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
50 of time values each suffixed by a time unit. Example:
</para>
52 <programlisting>2h
30min
</programlisting>
54 <para>All specified time values are meant to be added up. The above hence refers to
150 minutes. Display is
55 locale-independent, only English names for the time units are used.
</para>
59 <title>Parsing Time Spans
</title>
61 <para>When parsing, systemd will accept the same time span syntax.
62 Separating spaces may be omitted. The following time units are
66 <listitem><para>usec, us
</para></listitem>
67 <listitem><para>msec, ms
</para></listitem>
68 <listitem><para>seconds, second, sec, s
</para></listitem>
69 <listitem><para>minutes, minute, min, m
</para></listitem>
70 <listitem><para>hours, hour, hr, h
</para></listitem>
71 <listitem><para>days, day, d
</para></listitem>
72 <listitem><para>weeks, week, w
</para></listitem>
73 <listitem><para>months, month, M (defined as
30.44 days)
</para></listitem>
74 <listitem><para>years, year, y (defined as
365.25 days)
</para></listitem>
77 <para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
78 such. In a few cases
<literal>ns
</literal>,
<literal>nsec
</literal> is accepted too, where the granularity of the
79 time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
82 <para>Examples for valid time span specifications:
</para>
89 300ms20s
5day
</programlisting>
93 <title>Displaying Timestamps
</title>
95 <para>Timestamps refer to specific, unique points in time. On
96 display, systemd will format these in the local timezone as
99 <programlisting>Fri
2012-
11-
23 23:
02:
15 CET
</programlisting>
101 <para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.
</para>
103 <para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
104 the
<literal>UTC
</literal> timezone specifier in the output.
</para>
106 <para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
107 separated by a full stop from the seconds component.
</para>
111 <title>Parsing Timestamps
</title>
113 <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
114 as the literal string
<literal>UTC
</literal> (for the UTC timezone), or is specified to be the locally configured
115 timezone, or the timezone name in the IANA timezone database format. The complete list of timezones
116 supported on your system can be obtained using the
<literal>timedatectl list-timezones
</literal>
117 (see
<citerefentry><refentrytitle>timedatectl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
118 Using IANA format is recommended over local timezone names, as less prone to errors (eg: with local timezone it's possible to
119 specify daylight saving time in winter, while it's incorrect). The weekday specification is optional, but when
120 the weekday is specified, it must either be in the abbreviated (
<literal>Wed
</literal>) or non-abbreviated
121 (
<literal>Wednesday
</literal>) English language form (case does not matter), and is not subject to the locale
122 choice of the user. Either the date, or the time part may be omitted, in which case the current date or
00:
00:
00,
123 respectively, is assumed. The seconds component of the time may also be omitted, in which case
":00" is
124 assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).
</para>
126 <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
129 <para>When parsing, systemd will also accept a few special
130 placeholders instead of timestamps:
<literal>now
</literal> may be
131 used to refer to the current time (or of the invocation of the
132 command that is currently executed).
<literal>today
</literal>,
133 <literal>yesterday
</literal>, and
<literal>tomorrow
</literal> refer to
134 00:
00:
00 of the current day, the day before, or the next day,
137 <para>When parsing, systemd will also accept relative time
138 specifications. A time span (see above) that is prefixed with
139 <literal>+
</literal> is evaluated to the current time plus the
140 specified time span. Correspondingly, a time span that is prefixed
141 with
<literal>-
</literal> is evaluated to the current time minus
142 the specified time span. Instead of prefixing the time span with
143 <literal>+
</literal> or
<literal>-
</literal>, it may also be
144 suffixed with a space and the word
<literal>left
</literal> or
145 <literal>ago
</literal>.
</para>
147 <para>Finally, a timespan prefixed with
<literal>@
</literal> is
148 evaluated relative to the UNIX time epoch
1st Jan,
1970,
151 <para>Examples for valid timestamps and their normalized form
152 (assuming the current time was
2012-
11-
23 18:
15:
22 and the timezone
153 was UTC+
8, for example TZ=Asia/Shanghai):
</para>
155 <programlisting> Fri
2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
156 2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
157 2012-
11-
23 11:
12:
13 UTC → Fri
2012-
11-
23 19:
12:
13
158 2012-
11-
23 → Fri
2012-
11-
23 00:
00:
00
159 12-
11-
23 → Fri
2012-
11-
23 00:
00:
00
160 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
161 11:
12 → Fri
2012-
11-
23 11:
12:
00
162 now → Fri
2012-
11-
23 18:
15:
22
163 today → Fri
2012-
11-
23 00:
00:
00
164 today UTC → Fri
2012-
11-
23 16:
00:
00
165 yesterday → Fri
2012-
11-
22 00:
00:
00
166 tomorrow → Fri
2012-
11-
24 00:
00:
00
167 tomorrow Pacific/Auckland → Thu
2012-
11-
23 19:
00:
00
168 +
3h30min → Fri
2012-
11-
23 21:
45:
22
169 -
5s → Fri
2012-
11-
23 18:
15:
17
170 11min ago → Fri
2012-
11-
23 18:
04:
22
171 @
1395716396 → Tue
2014-
03-
25 03:
59:
56</programlisting>
173 <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
174 locally, as the timezone component is not understood (unless it happens to be
<literal>UTC
</literal>).
</para>
176 <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
177 by a full stop from the seconds component. Example:
</para>
179 <programlisting>2014-
03-
25 03:
59:
56.654563</programlisting>
181 <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
182 invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
183 timestamp is formatted as follows:
</para>
185 <programlisting>2 months
5 days ago
</programlisting>
187 <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).
</para>
191 <title>Calendar Events
</title>
193 <para>Calendar events may be used to refer to one or more points
194 in time in a single expression. They form a superset of the
195 absolute timestamps explained above:
</para>
197 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
199 <para>The above refers to
11:
12:
13 of the first or fifth day of
200 any month of the year
2012, but only if that day is a Thursday or
203 <para>The weekday specification is optional. If specified, it
204 should consist of one or more English language weekday names,
205 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
206 form (case does not matter), separated by commas. Specifying two
207 weekdays separated by
<literal>..
</literal> refers to a range of
208 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
209 may be combined freely.
</para>
211 <para>In the date and time specifications, any component may be
212 specified as
<literal>*
</literal> in which case any value will
213 match. Alternatively, each component can be specified as a list of
214 values separated by commas. Values may be suffixed with
215 <literal>/
</literal> and a repetition value, which indicates that
216 the value itself and the value plus all multiples of the repetition value
217 are matched. Two values separated by
<literal>..
</literal> may be used
218 to indicate a range of values; ranges may also be followed with
219 <literal>/
</literal> and a repetition value.
</para>
221 <para>A date specification may use
<literal>~
</literal> to indicate the
222 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
223 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
224 means
"the last Monday in May."</para>
226 <para>The seconds component may contain decimal fractions both in
227 the value and the repetition. All fractions are rounded to
6
228 decimal places.
</para>
230 <para>Either time or date specification may be omitted, in which
231 case the current day and
00:
00:
00 is implied, respectively. If the
232 second component is not specified,
<literal>:
00</literal> is
235 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
236 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
237 in the IANA timezone database format (also see above).
</para>
239 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
241 <programlisting> minutely → *-*-* *:*:
00
242 hourly → *-*-* *:
00:
00
243 daily → *-*-*
00:
00:
00
244 monthly → *-*-
01 00:
00:
00
245 weekly → Mon *-*-*
00:
00:
00
246 yearly → *-
01-
01 00:
00:
00
247 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
248 semiannually → *-
01,
07-
01 00:
00:
00
251 <para>Examples for valid timestamps and their
252 normalized form:
</para>
254 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
255 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
256 Wed *-
1 → Wed *-*-
01 00:
00:
00
257 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
258 Wed,
17:
48 → Wed *-*-*
17:
48:
00
259 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
260 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
261 10-
15 → *-
10-
15 00:
00:
00
262 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
263 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
264 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
265 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
266 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
267 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
268 08:
05:
40 → *-*-*
08:
05:
40
269 05:
40 → *-*-*
05:
40:
00
270 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
271 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
272 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
273 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
274 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
275 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
276 2003-
03-
05 →
2003-
03-
05 00:
00:
00
277 03-
05 → *-
03-
05 00:
00:
00
278 hourly → *-*-* *:
00:
00
279 daily → *-*-*
00:
00:
00
280 daily UTC → *-*-*
00:
00:
00 UTC
281 monthly → *-*-
01 00:
00:
00
282 weekly → Mon *-*-*
00:
00:
00
283 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
284 yearly → *-
01-
01 00:
00:
00
285 annually → *-
01-
01 00:
00:
00
286 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
288 <para>Calendar events are used by timer units, see
289 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
292 <para>Use the
<command>calendar
</command> command of
293 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
294 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
295 calendar event would elapse next.
</para>
299 <title>See Also
</title>
301 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
302 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
303 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
304 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
305 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
306 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>