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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
102 it is given as the literal string
<literal>UTC
</literal> (for the UTC timezone), or is specified to be
103 the locally configured timezone, or the timezone name in the IANA timezone database format. The complete
104 list of timezones supported on your system can be obtained using the
<literal>timedatectl
105 list-timezones
</literal> (see
106 <citerefentry><refentrytitle>timedatectl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Using
107 IANA format is recommended over local timezone names, as less prone to errors (e.g. with local timezone
108 it's possible to specify daylight saving time in winter, even though that is not correct). The weekday
109 specification is optional, but when the weekday is specified, it must either be in the abbreviated
110 (
<literal>Wed
</literal>) or non-abbreviated (
<literal>Wednesday
</literal>) English language form (case
111 does not matter), and is not subject to the locale choice of the user. Either the date, or the time part
112 may be omitted, in which case the current date or
00:
00:
00, respectively, is assumed. The seconds
113 component of the time may also be omitted, in which case
":00" is assumed. Year numbers may be specified
114 in full or may be abbreviated (omitting the century).
</para>
116 <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
119 <para>When parsing, systemd will also accept a few special
120 placeholders instead of timestamps:
<literal>now
</literal> may be
121 used to refer to the current time (or of the invocation of the
122 command that is currently executed).
<literal>today
</literal>,
123 <literal>yesterday
</literal>, and
<literal>tomorrow
</literal> refer to
124 00:
00:
00 of the current day, the day before, or the next day,
127 <para>When parsing, systemd will also accept relative time
128 specifications. A time span (see above) that is prefixed with
129 <literal>+
</literal> is evaluated to the current time plus the
130 specified time span. Correspondingly, a time span that is prefixed
131 with
<literal>-
</literal> is evaluated to the current time minus
132 the specified time span. Instead of prefixing the time span with
133 <literal>+
</literal> or
<literal>-
</literal>, it may also be
134 suffixed with a space and the word
<literal>left
</literal> or
135 <literal>ago
</literal>.
</para>
137 <para>Finally, a timespan prefixed with
<literal>@
</literal> is
138 evaluated relative to the UNIX time epoch
1st Jan,
1970,
141 <para>Examples for valid timestamps and their normalized form (assuming the current time was
2012-
11-
23
142 18:
15:
22 and the timezone was UTC+
8, for example
<literal>TZ=:Asia/Shanghai
</literal>):
</para>
144 <programlisting> Fri
2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
145 2012-
11-
23 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
146 2012-
11-
23 11:
12:
13 UTC → Fri
2012-
11-
23 19:
12:
13
147 2012-
11-
23 → Fri
2012-
11-
23 00:
00:
00
148 12-
11-
23 → Fri
2012-
11-
23 00:
00:
00
149 11:
12:
13 → Fri
2012-
11-
23 11:
12:
13
150 11:
12 → Fri
2012-
11-
23 11:
12:
00
151 now → Fri
2012-
11-
23 18:
15:
22
152 today → Fri
2012-
11-
23 00:
00:
00
153 today UTC → Fri
2012-
11-
23 16:
00:
00
154 yesterday → Fri
2012-
11-
22 00:
00:
00
155 tomorrow → Fri
2012-
11-
24 00:
00:
00
156 tomorrow Pacific/Auckland → Thu
2012-
11-
23 19:
00:
00
157 +
3h30min → Fri
2012-
11-
23 21:
45:
22
158 -
5s → Fri
2012-
11-
23 18:
15:
17
159 11min ago → Fri
2012-
11-
23 18:
04:
22
160 @
1395716396 → Tue
2014-
03-
25 03:
59:
56</programlisting>
162 <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
163 locally, as the timezone component is not understood (unless it happens to be
<literal>UTC
</literal>).
</para>
165 <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
166 by a full stop from the seconds component. Example:
</para>
168 <programlisting>2014-
03-
25 03:
59:
56.654563</programlisting>
170 <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
171 invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
172 timestamp is formatted as follows:
</para>
174 <programlisting>2 months
5 days ago
</programlisting>
176 <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).
</para>
178 <para>Use the
<command>timestamp
</command> command of
179 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
180 validate and normalize timestamps for testing purposes.
</para>
184 <title>Calendar Events
</title>
186 <para>Calendar events may be used to refer to one or more points
187 in time in a single expression. They form a superset of the
188 absolute timestamps explained above:
</para>
190 <programlisting>Thu,Fri
2012-*-
1,
5 11:
12:
13</programlisting>
192 <para>The above refers to
11:
12:
13 of the first or fifth day of
193 any month of the year
2012, but only if that day is a Thursday or
196 <para>The weekday specification is optional. If specified, it
197 should consist of one or more English language weekday names,
198 either in the abbreviated (Wed) or non-abbreviated (Wednesday)
199 form (case does not matter), separated by commas. Specifying two
200 weekdays separated by
<literal>..
</literal> refers to a range of
201 continuous weekdays.
<literal>,
</literal> and
<literal>..
</literal>
202 may be combined freely.
</para>
204 <para>In the date and time specifications, any component may be specified as
<literal>*
</literal> in
205 which case any value will match. Alternatively, each component can be specified as a list of values
206 separated by commas. Values may be suffixed with
<literal>/
</literal> and a repetition value, which
207 indicates that the value itself and the value plus all multiples of the repetition value are matched.
208 Two values separated by
<literal>..
</literal> may be used to indicate a range of values; ranges may also
209 be followed with
<literal>/
</literal> and a repetition value, in which case the expression matches all
210 times starting with the start value, and continuing with all multiples of the repetition value relative
211 to the start value, ending at the end value the latest.
</para>
213 <para>A date specification may use
<literal>~
</literal> to indicate the
214 last day(s) in a month. For example,
<literal>*-
02~
03</literal> means
215 "the third last day in February," and
<literal>Mon *-
05~
07/
1</literal>
216 means
"the last Monday in May."</para>
218 <para>The seconds component may contain decimal fractions both in
219 the value and the repetition. All fractions are rounded to
6
220 decimal places.
</para>
222 <para>Either time or date specification may be omitted, in which
223 case the current day and
00:
00:
00 is implied, respectively. If the
224 second component is not specified,
<literal>:
00</literal> is
227 <para>Timezone can be specified as the literal string
<literal>UTC
</literal>, or
228 the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
229 in the IANA timezone database format (also see above).
</para>
231 <para>The following special expressions may be used as shorthands for longer normalized forms:
</para>
233 <programlisting> minutely → *-*-* *:*:
00
234 hourly → *-*-* *:
00:
00
235 daily → *-*-*
00:
00:
00
236 monthly → *-*-
01 00:
00:
00
237 weekly → Mon *-*-*
00:
00:
00
238 yearly → *-
01-
01 00:
00:
00
239 quarterly → *-
01,
04,
07,
10-
01 00:
00:
00
240 semiannually → *-
01,
07-
01 00:
00:
00
243 <para>Examples for valid timestamps and their
244 normalized form:
</para>
246 <programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-*
00:
00:
00
247 Mon,Sun
12-*-*
2,
1:
23 → Mon,Sun
2012-*-*
01,
02:
23:
00
248 Wed *-
1 → Wed *-*-
01 00:
00:
00
249 Wed..Wed,Wed *-
1 → Wed *-*-
01 00:
00:
00
250 Wed,
17:
48 → Wed *-*-*
17:
48:
00
251 Wed..Sat,Tue
12-
10-
15 1:
2:
3 → Tue..Sat
2012-
10-
15 01:
02:
03
252 *-*-
7 0:
0:
0 → *-*-
07 00:
00:
00
253 10-
15 → *-
10-
15 00:
00:
00
254 monday *-
12-*
17:
00 → Mon *-
12-*
17:
00:
00
255 Mon,Fri *-*-
3,
1,
2 *:
30:
45 → Mon,Fri *-*-
01,
02,
03 *:
30:
45
256 12,
14,
13,
12:
20,
10,
30 → *-*-*
12,
13,
14:
10,
20,
30:
00
257 12.
.14:
10,
20,
30 → *-*-*
12.
.14:
10,
20,
30:
00
258 mon,fri *-
1/
2-
1,
3 *:
30:
45 → Mon,Fri *-
01/
2-
01,
03 *:
30:
45
259 03-
05 08:
05:
40 → *-
03-
05 08:
05:
40
260 08:
05:
40 → *-*-*
08:
05:
40
261 05:
40 → *-*-*
05:
40:
00
262 Sat,Sun
12-
05 08:
05:
40 → Sat,Sun *-
12-
05 08:
05:
40
263 Sat,Sun
08:
05:
40 → Sat,Sun *-*-*
08:
05:
40
264 2003-
03-
05 05:
40 →
2003-
03-
05 05:
40:
00
265 05:
40:
23.4200004/
3.1700005 → *-*-*
05:
40:
23.420000/
3.170001
266 2003-
02.
.04-
05 →
2003-
02.
.04-
05 00:
00:
00
267 2003-
03-
05 05:
40 UTC →
2003-
03-
05 05:
40:
00 UTC
268 2003-
03-
05 →
2003-
03-
05 00:
00:
00
269 03-
05 → *-
03-
05 00:
00:
00
270 hourly → *-*-* *:
00:
00
271 daily → *-*-*
00:
00:
00
272 daily UTC → *-*-*
00:
00:
00 UTC
273 monthly → *-*-
01 00:
00:
00
274 weekly → Mon *-*-*
00:
00:
00
275 weekly Pacific/Auckland → Mon *-*-*
00:
00:
00 Pacific/Auckland
276 yearly → *-
01-
01 00:
00:
00
277 annually → *-
01-
01 00:
00:
00
278 *:
2/
3 → *-*-* *:
02/
3:
00</programlisting>
280 <para>Calendar events are used by timer units, see
281 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
284 <para>Use the
<command>calendar
</command> command of
285 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
286 and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
287 calendar event would occur next.
</para>
291 <title>See Also
</title>
293 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
294 <citerefentry><refentrytitle>journalctl
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
295 <citerefentry><refentrytitle>systemd.timer
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
296 <citerefentry><refentrytitle>systemd.unit
</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
297 <citerefentry><refentrytitle>systemd.directives
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
298 <citerefentry><refentrytitle>systemd-analyze
</refentrytitle><manvolnum>1</manvolnum></citerefentry>