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1.0'
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2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
6 <refentry id=
"systemd.time">
9 <title>systemd.time
</title>
10 <productname>systemd
</productname>
14 <refentrytitle>systemd.time
</refentrytitle>
15 <manvolnum>7</manvolnum>
19 <refname>systemd.time
</refname>
20 <refpurpose>Time and date specifications
</refpurpose>
24 <title>Description
</title>
26 <para>In systemd, timestamps, time spans, and calendar events are
27 displayed and may be specified in closely related syntaxes.
</para>
31 <title>Displaying Time Spans
</title>
33 <para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
34 of time values each suffixed by a time unit. Example:
</para>
36 <programlisting>2h
30min
</programlisting>
38 <para>All specified time values are meant to be added up. The above hence refers to
150 minutes. Display is
39 locale-independent, only English names for the time units are used.
</para>
43 <title>Parsing Time Spans
</title>
45 <para>When parsing, systemd will accept the same time span syntax.
46 Separating spaces may be omitted. The following time units are
50 <listitem><para>usec, us, µs
</para></listitem>
51 <listitem><para>msec, ms
</para></listitem>
52 <listitem><para>seconds, second, sec, s
</para></listitem>
53 <listitem><para>minutes, minute, min, m
</para></listitem>
54 <listitem><para>hours, hour, hr, h
</para></listitem>
55 <listitem><para>days, day, d
</para></listitem>
56 <listitem><para>weeks, week, w
</para></listitem>
57 <listitem><para>months, month, M (defined as
30.44 days)
</para></listitem>
58 <listitem><para>years, year, y (defined as
365.25 days)
</para></listitem>
61 <para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
62 such. In a few cases
<literal>ns
</literal>,
<literal>nsec
</literal> is accepted too, where the granularity of the
63 time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
66 <para>Examples for valid time span specifications:
</para>
73 300ms20s
5day
</programlisting>
75 <para>One can use the
<command>timespan
</command> command of
76 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>
77 to normalise a textual time span for testing and validation purposes.
</para>
81 <title>Displaying Timestamps
</title>
83 <para>Timestamps refer to specific, unique points in time. On
84 display, systemd will format these in the local timezone as
87 <programlisting>Fri
2012-
11-
23 23:
02:
15 CET
</programlisting>
89 <para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.
</para>
91 <para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
92 the
<literal>UTC
</literal> timezone specifier in the output.
</para>
94 <para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
95 separated by a full stop from the seconds component.
</para>
99 <title>Parsing Timestamps
</title>
101 <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
102 as the literal string
<literal>UTC
</literal> (for the UTC timezone), or is specified to be the locally configured
103 timezone, or the timezone name in the IANA timezone database format. The complete list of timezones
104 supported on your system can be obtained using the
<literal>timedatectl list-timezones
</literal>
105 (see
<citerefentry><refentrytitle>timedatectl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
106 Using IANA format is recommended over local timezone names, as less prone to errors (eg: with local timezone it's possible to
107 specify daylight saving time in winter, while it's incorrect). The weekday specification is optional, but when
108 the weekday is specified, it must either be in the abbreviated (
<literal>Wed
</literal>) or non-abbreviated
109 (
<literal>Wednesday
</literal>) English language form (case does not matter), and is not subject to the locale
110 choice of the user. Either the date, or the time part may be omitted, in which case the current date or
00:
00:
00,
111 respectively, is assumed. The seconds component of the time may also be omitted, in which case
":00" is
112 assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).
</para>
114 <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
117 <para>When parsing, systemd will also accept a few special
118 placeholders instead of timestamps:
<literal>now
</literal> may be
119 used to refer to the current time (or of the invocation of the
120 command that is currently executed).
<literal>today
</literal>,
121 <literal>yesterday
</literal>, and
<literal>tomorrow
</literal> refer to
122 00:
00:
00 of the current day, the day before, or the next day,
125 <para>When parsing, systemd will also accept relative time
126 specifications. A time span (see above) that is prefixed with
127 <literal>+
</literal> is evaluated to the current time plus the
128 specified time span. Correspondingly, a time span that is prefixed
129 with
<literal>-
</literal> is evaluated to the current time minus
130 the specified time span. Instead of prefixing the time span with
131 <literal>+
</literal> or
<literal>-
</literal>, it may also be
132 suffixed with a space and the word
<literal>left
</literal> or
133 <literal>ago
</literal>.
</para>
135 <para>Finally, a timespan prefixed with
<literal>@
</literal> is
136 evaluated relative to the UNIX time epoch
1st Jan,
1970,
139 <para>Examples for valid timestamps and their normalized form
140 (assuming the current time was
2012-
11-
23 18:
15:
22 and the timezone
141 was UTC+
8, for example TZ=Asia/Shanghai):
</para>
143 <programlisting> Fri
2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
144 2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
145 2012-
11-
23 11:
12:
13 UTC → Fri
2012-
11-
23 19:
12:
13
146 2012-
11-
23 → Fri
2012-
11-
23 00:
00:
00
147 12-
11-
23 → Fri
2012-
11-
23 00:
00:
00
148 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
149 11:
12 → Fri
2012-
11-
23 11:
12:
00
150 now → Fri
2012-
11-
23 18:
15:
22
151 today → Fri
2012-
11-
23 00:
00:
00
152 today UTC → Fri
2012-
11-
23 16:
00:
00
153 yesterday → Fri
2012-
11-
22 00:
00:
00
154 tomorrow → Fri
2012-
11-
24 00:
00:
00
155 tomorrow Pacific/Auckland → Thu
2012-
11-
23 19:
00:
00
156 +
3h30min → Fri
2012-
11-
23 21:
45:
22
157 -
5s → Fri
2012-
11-
23 18:
15:
17
158 11min ago → Fri
2012-
11-
23 18:
04:
22
159 @
1395716396 → Tue
2014-
03-
25 03:
59:
56</programlisting>
161 <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
162 locally, as the timezone component is not understood (unless it happens to be
<literal>UTC
</literal>).
</para>
164 <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
165 by a full stop from the seconds component. Example:
</para>
167 <programlisting>2014-
03-
25 03:
59:
56.654563</programlisting>
169 <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
170 invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
171 timestamp is formatted as follows:
</para>
173 <programlisting>2 months
5 days ago
</programlisting>
175 <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).
</para>
179 <title>Calendar Events
</title>
181 <para>Calendar events may be used to refer to one or more points
182 in time in a single expression. They form a superset of the
183 absolute timestamps explained above:
</para>
185 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
187 <para>The above refers to
11:
12:
13 of the first or fifth day of
188 any month of the year
2012, but only if that day is a Thursday or
191 <para>The weekday specification is optional. If specified, it
192 should consist of one or more English language weekday names,
193 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
194 form (case does not matter), separated by commas. Specifying two
195 weekdays separated by
<literal>..
</literal> refers to a range of
196 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
197 may be combined freely.
</para>
199 <para>In the date and time specifications, any component may be
200 specified as
<literal>*
</literal> in which case any value will
201 match. Alternatively, each component can be specified as a list of
202 values separated by commas. Values may be suffixed with
203 <literal>/
</literal> and a repetition value, which indicates that
204 the value itself and the value plus all multiples of the repetition value
205 are matched. Two values separated by
<literal>..
</literal> may be used
206 to indicate a range of values; ranges may also be followed with
207 <literal>/
</literal> and a repetition value.
</para>
209 <para>A date specification may use
<literal>~
</literal> to indicate the
210 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
211 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
212 means
"the last Monday in May."</para>
214 <para>The seconds component may contain decimal fractions both in
215 the value and the repetition. All fractions are rounded to
6
216 decimal places.
</para>
218 <para>Either time or date specification may be omitted, in which
219 case the current day and
00:
00:
00 is implied, respectively. If the
220 second component is not specified,
<literal>:
00</literal> is
223 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
224 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
225 in the IANA timezone database format (also see above).
</para>
227 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
229 <programlisting> minutely → *-*-* *:*:
00
230 hourly → *-*-* *:
00:
00
231 daily → *-*-*
00:
00:
00
232 monthly → *-*-
01 00:
00:
00
233 weekly → Mon *-*-*
00:
00:
00
234 yearly → *-
01-
01 00:
00:
00
235 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
236 semiannually → *-
01,
07-
01 00:
00:
00
239 <para>Examples for valid timestamps and their
240 normalized form:
</para>
242 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
243 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
244 Wed *-
1 → Wed *-*-
01 00:
00:
00
245 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
246 Wed,
17:
48 → Wed *-*-*
17:
48:
00
247 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
248 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
249 10-
15 → *-
10-
15 00:
00:
00
250 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
251 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
252 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
253 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
254 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
255 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
256 08:
05:
40 → *-*-*
08:
05:
40
257 05:
40 → *-*-*
05:
40:
00
258 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
259 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
260 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
261 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
262 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
263 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
264 2003-
03-
05 →
2003-
03-
05 00:
00:
00
265 03-
05 → *-
03-
05 00:
00:
00
266 hourly → *-*-* *:
00:
00
267 daily → *-*-*
00:
00:
00
268 daily UTC → *-*-*
00:
00:
00 UTC
269 monthly → *-*-
01 00:
00:
00
270 weekly → Mon *-*-*
00:
00:
00
271 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
272 yearly → *-
01-
01 00:
00:
00
273 annually → *-
01-
01 00:
00:
00
274 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
276 <para>Calendar events are used by timer units, see
277 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
280 <para>Use the
<command>calendar
</command> command of
281 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
282 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
283 calendar event would elapse next.
</para>
287 <title>See Also
</title>
289 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
290 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
291 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
292 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
293 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
294 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>