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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 (assuming the current time was
2012-
11-
23
140 18:
15:
22 and the timezone was UTC+
8, for example
<literal>TZ=:Asia/Shanghai
</literal>):
</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>
176 <para>Use the
<command>timestamp
</command> command of
177 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
178 validate and normalize timestamps for testing purposes.
</para>
182 <title>Calendar Events
</title>
184 <para>Calendar events may be used to refer to one or more points
185 in time in a single expression. They form a superset of the
186 absolute timestamps explained above:
</para>
188 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
190 <para>The above refers to
11:
12:
13 of the first or fifth day of
191 any month of the year
2012, but only if that day is a Thursday or
194 <para>The weekday specification is optional. If specified, it
195 should consist of one or more English language weekday names,
196 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
197 form (case does not matter), separated by commas. Specifying two
198 weekdays separated by
<literal>..
</literal> refers to a range of
199 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
200 may be combined freely.
</para>
202 <para>In the date and time specifications, any component may be
203 specified as
<literal>*
</literal> in which case any value will
204 match. Alternatively, each component can be specified as a list of
205 values separated by commas. Values may be suffixed with
206 <literal>/
</literal> and a repetition value, which indicates that
207 the value itself and the value plus all multiples of the repetition value
208 are matched. Two values separated by
<literal>..
</literal> may be used
209 to indicate a range of values; ranges may also be followed with
210 <literal>/
</literal> and a repetition value.
</para>
212 <para>A date specification may use
<literal>~
</literal> to indicate the
213 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
214 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
215 means
"the last Monday in May."</para>
217 <para>The seconds component may contain decimal fractions both in
218 the value and the repetition. All fractions are rounded to
6
219 decimal places.
</para>
221 <para>Either time or date specification may be omitted, in which
222 case the current day and
00:
00:
00 is implied, respectively. If the
223 second component is not specified,
<literal>:
00</literal> is
226 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
227 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
228 in the IANA timezone database format (also see above).
</para>
230 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
232 <programlisting> minutely → *-*-* *:*:
00
233 hourly → *-*-* *:
00:
00
234 daily → *-*-*
00:
00:
00
235 monthly → *-*-
01 00:
00:
00
236 weekly → Mon *-*-*
00:
00:
00
237 yearly → *-
01-
01 00:
00:
00
238 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
239 semiannually → *-
01,
07-
01 00:
00:
00
242 <para>Examples for valid timestamps and their
243 normalized form:
</para>
245 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
246 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
247 Wed *-
1 → Wed *-*-
01 00:
00:
00
248 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
249 Wed,
17:
48 → Wed *-*-*
17:
48:
00
250 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
251 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
252 10-
15 → *-
10-
15 00:
00:
00
253 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
254 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
255 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
256 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
257 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
258 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
259 08:
05:
40 → *-*-*
08:
05:
40
260 05:
40 → *-*-*
05:
40:
00
261 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
262 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
263 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
264 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
265 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
266 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
267 2003-
03-
05 →
2003-
03-
05 00:
00:
00
268 03-
05 → *-
03-
05 00:
00:
00
269 hourly → *-*-* *:
00:
00
270 daily → *-*-*
00:
00:
00
271 daily UTC → *-*-*
00:
00:
00 UTC
272 monthly → *-*-
01 00:
00:
00
273 weekly → Mon *-*-*
00:
00:
00
274 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
275 yearly → *-
01-
01 00:
00:
00
276 annually → *-
01-
01 00:
00:
00
277 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
279 <para>Calendar events are used by timer units, see
280 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
283 <para>Use the
<command>calendar
</command> command of
284 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
285 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
286 calendar event would elapse next.
</para>
290 <title>See Also
</title>
292 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
293 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
294 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
295 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
296 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
297 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>