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 Copyright 2010 Lennart Poettering
11 <refentry id=
"systemd.time">
14 <title>systemd.time
</title>
15 <productname>systemd
</productname>
19 <contrib>Developer
</contrib>
20 <firstname>Lennart
</firstname>
21 <surname>Poettering
</surname>
22 <email>lennart@poettering.net
</email>
28 <refentrytitle>systemd.time
</refentrytitle>
29 <manvolnum>7</manvolnum>
33 <refname>systemd.time
</refname>
34 <refpurpose>Time and date specifications
</refpurpose>
38 <title>Description
</title>
40 <para>In systemd, timestamps, time spans, and calendar events are
41 displayed and may be specified in closely related syntaxes.
</para>
45 <title>Displaying Time Spans
</title>
47 <para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
48 of time values each suffixed by a time unit. Example:
</para>
50 <programlisting>2h
30min
</programlisting>
52 <para>All specified time values are meant to be added up. The above hence refers to
150 minutes. Display is
53 locale-independent, only English names for the time units are used.
</para>
57 <title>Parsing Time Spans
</title>
59 <para>When parsing, systemd will accept the same time span syntax.
60 Separating spaces may be omitted. The following time units are
64 <listitem><para>usec, us
</para></listitem>
65 <listitem><para>msec, ms
</para></listitem>
66 <listitem><para>seconds, second, sec, s
</para></listitem>
67 <listitem><para>minutes, minute, min, m
</para></listitem>
68 <listitem><para>hours, hour, hr, h
</para></listitem>
69 <listitem><para>days, day, d
</para></listitem>
70 <listitem><para>weeks, week, w
</para></listitem>
71 <listitem><para>months, month, M (defined as
30.44 days)
</para></listitem>
72 <listitem><para>years, year, y (defined as
365.25 days)
</para></listitem>
75 <para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
76 such. In a few cases
<literal>ns
</literal>,
<literal>nsec
</literal> is accepted too, where the granularity of the
77 time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
80 <para>Examples for valid time span specifications:
</para>
87 300ms20s
5day
</programlisting>
91 <title>Displaying Timestamps
</title>
93 <para>Timestamps refer to specific, unique points in time. On
94 display, systemd will format these in the local timezone as
97 <programlisting>Fri
2012-
11-
23 23:
02:
15 CET
</programlisting>
99 <para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.
</para>
101 <para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
102 the
<literal>UTC
</literal> timezone specifier in the output.
</para>
104 <para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
105 separated by a full stop from the seconds component.
</para>
109 <title>Parsing Timestamps
</title>
111 <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
112 as the literal string
<literal>UTC
</literal> (for the UTC timezone), or is specified to be the locally configured
113 timezone, or the timezone name in the IANA timezone database format. The complete list of timezones
114 supported on your system can be obtained using the
<literal>timedatectl list-timezones
</literal>
115 (see
<citerefentry><refentrytitle>timedatectl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
116 Using IANA format is recommended over local timezone names, as less prone to errors (eg: with local timezone it's possible to
117 specify daylight saving time in winter, while it's incorrect). The weekday specification is optional, but when
118 the weekday is specified, it must either be in the abbreviated (
<literal>Wed
</literal>) or non-abbreviated
119 (
<literal>Wednesday
</literal>) English language form (case does not matter), and is not subject to the locale
120 choice of the user. Either the date, or the time part may be omitted, in which case the current date or
00:
00:
00,
121 respectively, is assumed. The seconds component of the time may also be omitted, in which case
":00" is
122 assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).
</para>
124 <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
127 <para>When parsing, systemd will also accept a few special
128 placeholders instead of timestamps:
<literal>now
</literal> may be
129 used to refer to the current time (or of the invocation of the
130 command that is currently executed).
<literal>today
</literal>,
131 <literal>yesterday
</literal>, and
<literal>tomorrow
</literal> refer to
132 00:
00:
00 of the current day, the day before, or the next day,
135 <para>When parsing, systemd will also accept relative time
136 specifications. A time span (see above) that is prefixed with
137 <literal>+
</literal> is evaluated to the current time plus the
138 specified time span. Correspondingly, a time span that is prefixed
139 with
<literal>-
</literal> is evaluated to the current time minus
140 the specified time span. Instead of prefixing the time span with
141 <literal>+
</literal> or
<literal>-
</literal>, it may also be
142 suffixed with a space and the word
<literal>left
</literal> or
143 <literal>ago
</literal>.
</para>
145 <para>Finally, a timespan prefixed with
<literal>@
</literal> is
146 evaluated relative to the UNIX time epoch
1st Jan,
1970,
149 <para>Examples for valid timestamps and their normalized form
150 (assuming the current time was
2012-
11-
23 18:
15:
22 and the timezone
151 was UTC+
8, for example TZ=Asia/Shanghai):
</para>
153 <programlisting> Fri
2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
154 2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
155 2012-
11-
23 11:
12:
13 UTC → Fri
2012-
11-
23 19:
12:
13
156 2012-
11-
23 → Fri
2012-
11-
23 00:
00:
00
157 12-
11-
23 → Fri
2012-
11-
23 00:
00:
00
158 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
159 11:
12 → Fri
2012-
11-
23 11:
12:
00
160 now → Fri
2012-
11-
23 18:
15:
22
161 today → Fri
2012-
11-
23 00:
00:
00
162 today UTC → Fri
2012-
11-
23 16:
00:
00
163 yesterday → Fri
2012-
11-
22 00:
00:
00
164 tomorrow → Fri
2012-
11-
24 00:
00:
00
165 tomorrow Pacific/Auckland → Thu
2012-
11-
23 19:
00:
00
166 +
3h30min → Fri
2012-
11-
23 21:
45:
22
167 -
5s → Fri
2012-
11-
23 18:
15:
17
168 11min ago → Fri
2012-
11-
23 18:
04:
22
169 @
1395716396 → Tue
2014-
03-
25 03:
59:
56</programlisting>
171 <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
172 locally, as the timezone component is not understood (unless it happens to be
<literal>UTC
</literal>).
</para>
174 <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
175 by a full stop from the seconds component. Example:
</para>
177 <programlisting>2014-
03-
25 03:
59:
56.654563</programlisting>
179 <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
180 invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
181 timestamp is formatted as follows:
</para>
183 <programlisting>2 months
5 days ago
</programlisting>
185 <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).
</para>
189 <title>Calendar Events
</title>
191 <para>Calendar events may be used to refer to one or more points
192 in time in a single expression. They form a superset of the
193 absolute timestamps explained above:
</para>
195 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
197 <para>The above refers to
11:
12:
13 of the first or fifth day of
198 any month of the year
2012, but only if that day is a Thursday or
201 <para>The weekday specification is optional. If specified, it
202 should consist of one or more English language weekday names,
203 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
204 form (case does not matter), separated by commas. Specifying two
205 weekdays separated by
<literal>..
</literal> refers to a range of
206 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
207 may be combined freely.
</para>
209 <para>In the date and time specifications, any component may be
210 specified as
<literal>*
</literal> in which case any value will
211 match. Alternatively, each component can be specified as a list of
212 values separated by commas. Values may be suffixed with
213 <literal>/
</literal> and a repetition value, which indicates that
214 the value itself and the value plus all multiples of the repetition value
215 are matched. Two values separated by
<literal>..
</literal> may be used
216 to indicate a range of values; ranges may also be followed with
217 <literal>/
</literal> and a repetition value.
</para>
219 <para>A date specification may use
<literal>~
</literal> to indicate the
220 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
221 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
222 means
"the last Monday in May."</para>
224 <para>The seconds component may contain decimal fractions both in
225 the value and the repetition. All fractions are rounded to
6
226 decimal places.
</para>
228 <para>Either time or date specification may be omitted, in which
229 case the current day and
00:
00:
00 is implied, respectively. If the
230 second component is not specified,
<literal>:
00</literal> is
233 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
234 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
235 in the IANA timezone database format (also see above).
</para>
237 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
239 <programlisting> minutely → *-*-* *:*:
00
240 hourly → *-*-* *:
00:
00
241 daily → *-*-*
00:
00:
00
242 monthly → *-*-
01 00:
00:
00
243 weekly → Mon *-*-*
00:
00:
00
244 yearly → *-
01-
01 00:
00:
00
245 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
246 semiannually → *-
01,
07-
01 00:
00:
00
249 <para>Examples for valid timestamps and their
250 normalized form:
</para>
252 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
253 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
254 Wed *-
1 → Wed *-*-
01 00:
00:
00
255 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
256 Wed,
17:
48 → Wed *-*-*
17:
48:
00
257 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
258 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
259 10-
15 → *-
10-
15 00:
00:
00
260 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
261 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
262 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
263 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
264 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
265 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
266 08:
05:
40 → *-*-*
08:
05:
40
267 05:
40 → *-*-*
05:
40:
00
268 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
269 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
270 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
271 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
272 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
273 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
274 2003-
03-
05 →
2003-
03-
05 00:
00:
00
275 03-
05 → *-
03-
05 00:
00:
00
276 hourly → *-*-* *:
00:
00
277 daily → *-*-*
00:
00:
00
278 daily UTC → *-*-*
00:
00:
00 UTC
279 monthly → *-*-
01 00:
00:
00
280 weekly → Mon *-*-*
00:
00:
00
281 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
282 yearly → *-
01-
01 00:
00:
00
283 annually → *-
01-
01 00:
00:
00
284 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
286 <para>Calendar events are used by timer units, see
287 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
290 <para>Use the
<command>calendar
</command> command of
291 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
292 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
293 calendar event would elapse next.
</para>
297 <title>See Also
</title>
299 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
300 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
301 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
302 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
303 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
304 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>