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1.0'
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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+
9 <refentry id=
"systemd.time">
12 <title>systemd.time
</title>
13 <productname>systemd
</productname>
17 <contrib>Developer
</contrib>
18 <firstname>Lennart
</firstname>
19 <surname>Poettering
</surname>
20 <email>lennart@poettering.net
</email>
26 <refentrytitle>systemd.time
</refentrytitle>
27 <manvolnum>7</manvolnum>
31 <refname>systemd.time
</refname>
32 <refpurpose>Time and date specifications
</refpurpose>
36 <title>Description
</title>
38 <para>In systemd, timestamps, time spans, and calendar events are
39 displayed and may be specified in closely related syntaxes.
</para>
43 <title>Displaying Time Spans
</title>
45 <para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
46 of time values each suffixed by a time unit. Example:
</para>
48 <programlisting>2h
30min
</programlisting>
50 <para>All specified time values are meant to be added up. The above hence refers to
150 minutes. Display is
51 locale-independent, only English names for the time units are used.
</para>
55 <title>Parsing Time Spans
</title>
57 <para>When parsing, systemd will accept the same time span syntax.
58 Separating spaces may be omitted. The following time units are
62 <listitem><para>usec, us
</para></listitem>
63 <listitem><para>msec, ms
</para></listitem>
64 <listitem><para>seconds, second, sec, s
</para></listitem>
65 <listitem><para>minutes, minute, min, m
</para></listitem>
66 <listitem><para>hours, hour, hr, h
</para></listitem>
67 <listitem><para>days, day, d
</para></listitem>
68 <listitem><para>weeks, week, w
</para></listitem>
69 <listitem><para>months, month, M (defined as
30.44 days)
</para></listitem>
70 <listitem><para>years, year, y (defined as
365.25 days)
</para></listitem>
73 <para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
74 such. In a few cases
<literal>ns
</literal>,
<literal>nsec
</literal> is accepted too, where the granularity of the
75 time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
78 <para>Examples for valid time span specifications:
</para>
85 300ms20s
5day
</programlisting>
89 <title>Displaying Timestamps
</title>
91 <para>Timestamps refer to specific, unique points in time. On
92 display, systemd will format these in the local timezone as
95 <programlisting>Fri
2012-
11-
23 23:
02:
15 CET
</programlisting>
97 <para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.
</para>
99 <para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
100 the
<literal>UTC
</literal> timezone specifier in the output.
</para>
102 <para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
103 separated by a full stop from the seconds component.
</para>
107 <title>Parsing Timestamps
</title>
109 <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
110 as the literal string
<literal>UTC
</literal> (for the UTC timezone), or is specified to be the locally configured
111 timezone, or the timezone name in the IANA timezone database format. The complete list of timezones
112 supported on your system can be obtained using the
<literal>timedatectl list-timezones
</literal>
113 (see
<citerefentry><refentrytitle>timedatectl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
114 Using IANA format is recommended over local timezone names, as less prone to errors (eg: with local timezone it's possible to
115 specify daylight saving time in winter, while it's incorrect). The weekday specification is optional, but when
116 the weekday is specified, it must either be in the abbreviated (
<literal>Wed
</literal>) or non-abbreviated
117 (
<literal>Wednesday
</literal>) English language form (case does not matter), and is not subject to the locale
118 choice of the user. Either the date, or the time part may be omitted, in which case the current date or
00:
00:
00,
119 respectively, is assumed. The seconds component of the time may also be omitted, in which case
":00" is
120 assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).
</para>
122 <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
125 <para>When parsing, systemd will also accept a few special
126 placeholders instead of timestamps:
<literal>now
</literal> may be
127 used to refer to the current time (or of the invocation of the
128 command that is currently executed).
<literal>today
</literal>,
129 <literal>yesterday
</literal>, and
<literal>tomorrow
</literal> refer to
130 00:
00:
00 of the current day, the day before, or the next day,
133 <para>When parsing, systemd will also accept relative time
134 specifications. A time span (see above) that is prefixed with
135 <literal>+
</literal> is evaluated to the current time plus the
136 specified time span. Correspondingly, a time span that is prefixed
137 with
<literal>-
</literal> is evaluated to the current time minus
138 the specified time span. Instead of prefixing the time span with
139 <literal>+
</literal> or
<literal>-
</literal>, it may also be
140 suffixed with a space and the word
<literal>left
</literal> or
141 <literal>ago
</literal>.
</para>
143 <para>Finally, a timespan prefixed with
<literal>@
</literal> is
144 evaluated relative to the UNIX time epoch
1st Jan,
1970,
147 <para>Examples for valid timestamps and their normalized form
148 (assuming the current time was
2012-
11-
23 18:
15:
22 and the timezone
149 was UTC+
8, for example TZ=Asia/Shanghai):
</para>
151 <programlisting> Fri
2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
152 2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
153 2012-
11-
23 11:
12:
13 UTC → Fri
2012-
11-
23 19:
12:
13
154 2012-
11-
23 → Fri
2012-
11-
23 00:
00:
00
155 12-
11-
23 → Fri
2012-
11-
23 00:
00:
00
156 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
157 11:
12 → Fri
2012-
11-
23 11:
12:
00
158 now → Fri
2012-
11-
23 18:
15:
22
159 today → Fri
2012-
11-
23 00:
00:
00
160 today UTC → Fri
2012-
11-
23 16:
00:
00
161 yesterday → Fri
2012-
11-
22 00:
00:
00
162 tomorrow → Fri
2012-
11-
24 00:
00:
00
163 tomorrow Pacific/Auckland → Thu
2012-
11-
23 19:
00:
00
164 +
3h30min → Fri
2012-
11-
23 21:
45:
22
165 -
5s → Fri
2012-
11-
23 18:
15:
17
166 11min ago → Fri
2012-
11-
23 18:
04:
22
167 @
1395716396 → Tue
2014-
03-
25 03:
59:
56</programlisting>
169 <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
170 locally, as the timezone component is not understood (unless it happens to be
<literal>UTC
</literal>).
</para>
172 <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
173 by a full stop from the seconds component. Example:
</para>
175 <programlisting>2014-
03-
25 03:
59:
56.654563</programlisting>
177 <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
178 invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
179 timestamp is formatted as follows:
</para>
181 <programlisting>2 months
5 days ago
</programlisting>
183 <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).
</para>
187 <title>Calendar Events
</title>
189 <para>Calendar events may be used to refer to one or more points
190 in time in a single expression. They form a superset of the
191 absolute timestamps explained above:
</para>
193 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
195 <para>The above refers to
11:
12:
13 of the first or fifth day of
196 any month of the year
2012, but only if that day is a Thursday or
199 <para>The weekday specification is optional. If specified, it
200 should consist of one or more English language weekday names,
201 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
202 form (case does not matter), separated by commas. Specifying two
203 weekdays separated by
<literal>..
</literal> refers to a range of
204 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
205 may be combined freely.
</para>
207 <para>In the date and time specifications, any component may be
208 specified as
<literal>*
</literal> in which case any value will
209 match. Alternatively, each component can be specified as a list of
210 values separated by commas. Values may be suffixed with
211 <literal>/
</literal> and a repetition value, which indicates that
212 the value itself and the value plus all multiples of the repetition value
213 are matched. Two values separated by
<literal>..
</literal> may be used
214 to indicate a range of values; ranges may also be followed with
215 <literal>/
</literal> and a repetition value.
</para>
217 <para>A date specification may use
<literal>~
</literal> to indicate the
218 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
219 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
220 means
"the last Monday in May."</para>
222 <para>The seconds component may contain decimal fractions both in
223 the value and the repetition. All fractions are rounded to
6
224 decimal places.
</para>
226 <para>Either time or date specification may be omitted, in which
227 case the current day and
00:
00:
00 is implied, respectively. If the
228 second component is not specified,
<literal>:
00</literal> is
231 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
232 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
233 in the IANA timezone database format (also see above).
</para>
235 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
237 <programlisting> minutely → *-*-* *:*:
00
238 hourly → *-*-* *:
00:
00
239 daily → *-*-*
00:
00:
00
240 monthly → *-*-
01 00:
00:
00
241 weekly → Mon *-*-*
00:
00:
00
242 yearly → *-
01-
01 00:
00:
00
243 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
244 semiannually → *-
01,
07-
01 00:
00:
00
247 <para>Examples for valid timestamps and their
248 normalized form:
</para>
250 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
251 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
252 Wed *-
1 → Wed *-*-
01 00:
00:
00
253 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
254 Wed,
17:
48 → Wed *-*-*
17:
48:
00
255 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
256 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
257 10-
15 → *-
10-
15 00:
00:
00
258 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
259 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
260 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
261 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
262 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
263 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
264 08:
05:
40 → *-*-*
08:
05:
40
265 05:
40 → *-*-*
05:
40:
00
266 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
267 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
268 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
269 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
270 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
271 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
272 2003-
03-
05 →
2003-
03-
05 00:
00:
00
273 03-
05 → *-
03-
05 00:
00:
00
274 hourly → *-*-* *:
00:
00
275 daily → *-*-*
00:
00:
00
276 daily UTC → *-*-*
00:
00:
00 UTC
277 monthly → *-*-
01 00:
00:
00
278 weekly → Mon *-*-*
00:
00:
00
279 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
280 yearly → *-
01-
01 00:
00:
00
281 annually → *-
01-
01 00:
00:
00
282 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
284 <para>Calendar events are used by timer units, see
285 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
288 <para>Use the
<command>calendar
</command> command of
289 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
290 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
291 calendar event would elapse next.
</para>
295 <title>See Also
</title>
297 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
298 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
299 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
300 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
301 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
302 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>