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