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21b3a0fcd1
This patch improves parsing and generation of timestamps and calendar specifications in two ways: - The week day is now always printed in the abbreviated English form, instead of the locale's setting. This makes sure we can always parse the week day again, even if the locale is changed. Given that we don't follow locale settings for printing timestamps in any other way either (for example, we always use 24h syntax in order to make uniform parsing possible), it only makes sense to also stick to a generic, non-localized form for the timestamp, too. - When parsing a timestamp, the local timezone (in its DST or non-DST name) may be specified, in addition to "UTC". Other timezones are still not supported however (not because we wouldn't want to, but mostly because libc offers no nice API for that). In itself this brings no new features, however it ensures that any locally formatted timestamp's timezone is also parsable again. These two changes ensure that the output of format_timestamp() may always be passed to parse_timestamp() and results in the original input. The related flavours for usec/UTC also work accordingly. Calendar specifications are extended in a similar way. The man page is updated accordingly, in particular this removes the claim that timestamps systemd prints wouldn't be parsable by systemd. They are now. The man page previously showed invalid timestamps as examples. This has been removed, as the man page shouldn't be a unit test, where such negative examples would be useful. The man page also no longer mentions the names of internal functions, such as format_timestamp_us() or UNIX error codes such as EINVAL.
311 lines
14 KiB
XML
311 lines
14 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd.time">
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<refentryinfo>
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<title>systemd.time</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd.time</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.time</refname>
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<refpurpose>Time and date specifications</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>In systemd, timestamps, time spans, and calendar events are
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displayed and may be specified in closely related syntaxes.</para>
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</refsect1>
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<refsect1>
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<title>Displaying Time Spans</title>
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<para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
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of time values each suffixed by a time unit. Example:</para>
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<programlisting>2h 30min</programlisting>
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<para>All specified time values are meant to be added up. The above hence refers to 150 minutes. Display is
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locale-independent, only English names for the time units are used.</para>
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</refsect1>
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<refsect1>
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<title>Parsing Time Spans</title>
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<para>When parsing, systemd will accept the same time span syntax.
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Separating spaces may be omitted. The following time units are
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understood:</para>
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<itemizedlist>
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<listitem><para>usec, us</para></listitem>
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<listitem><para>msec, ms</para></listitem>
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<listitem><para>seconds, second, sec, s</para></listitem>
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<listitem><para>minutes, minute, min, m</para></listitem>
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<listitem><para>hours, hour, hr, h</para></listitem>
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<listitem><para>days, day, d</para></listitem>
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<listitem><para>weeks, week, w</para></listitem>
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<listitem><para>months, month, M (defined as 30.44 days)</para></listitem>
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<listitem><para>years, year, y (defined as 365.25 days)</para></listitem>
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</itemizedlist>
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<para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
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such. In a few cases <literal>ns</literal>, <literal>nsec</literal> is accepted too, where the granularity of the
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time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
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accepted.</para>
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<para>Examples for valid time span specifications:</para>
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<programlisting>2 h
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2hours
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48hr
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1y 12month
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55s500ms
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300ms20s 5day</programlisting>
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</refsect1>
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<refsect1>
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<title>Displaying Timestamps</title>
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<para>Timestamps refer to specific, unique points in time. On
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display, systemd will format these in the local timezone as
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follows:</para>
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<programlisting>Fri 2012-11-23 23:02:15 CET</programlisting>
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<para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.</para>
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<para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
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the <literal>UTC</literal> timezone specifier in the output.</para>
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<para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
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separated by a full stop from the seconds component.</para>
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</refsect1>
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<refsect1>
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<title>Parsing Timestamps</title>
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<para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless it is given
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as the literal string <literal>UTC</literal> (for the UTC timezone) or is specified to be the locally configured
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timezone. Other timezones than the local and UTC are not supported. The weekday specification is optional, but when
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the weekday is specified, it must either be in the abbreviated (<literal>Wed</literal>) or non-abbreviated
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(<literal>Wednesday</literal>) English language form (case does not matter), and is not subject to the locale
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choice of the user. Either the date, or the time part may be omitted, in which case the current date or 00:00:00,
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respectively, is assumed. The seconds component of the time may also be omitted, in which case ":00" is
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assumed. Year numbers may be specified in full or may be abbreviated (omitting the century).</para>
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<para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
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the week.</para>
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<para>When parsing, systemd will also accept a few special
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placeholders instead of timestamps: <literal>now</literal> may be
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used to refer to the current time (or of the invocation of the
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command that is currently executed). <literal>today</literal>,
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<literal>yesterday</literal>, and <literal>tomorrow</literal> refer to
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00:00:00 of the current day, the day before, or the next day,
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respectively.</para>
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<para>When parsing, systemd will also accept relative time
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specifications. A time span (see above) that is prefixed with
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<literal>+</literal> is evaluated to the current time plus the
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specified time span. Correspondingly, a time span that is prefixed
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with <literal>-</literal> is evaluated to the current time minus
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the specified time span. Instead of prefixing the time span with
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<literal>+</literal> or <literal>-</literal>, it may also be
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suffixed with a space and the word <literal>left</literal> or
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<literal>ago</literal>.</para>
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<para>Finally, a timespan prefixed with <literal>@</literal> is
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evaluated relative to the UNIX time epoch 1st Jan, 1970,
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00:00.</para>
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<para>Examples for valid timestamps and their normalized form
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(assuming the current time was 2012-11-23 18:15:22 and the timezone
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was UTC+8, for example TZ=Asia/Shanghai):</para>
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<programlisting>Fri 2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
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2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
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2012-11-23 11:12:13 UTC → Fri 2012-11-23 19:12:13
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2012-11-23 → Fri 2012-11-23 00:00:00
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12-11-23 → Fri 2012-11-23 00:00:00
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11:12:13 → Fri 2012-11-23 11:12:13
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11:12 → Fri 2012-11-23 11:12:00
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now → Fri 2012-11-23 18:15:22
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today → Fri 2012-11-23 00:00:00
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today UTC → Fri 2012-11-23 16:00:00
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yesterday → Fri 2012-11-22 00:00:00
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tomorrow → Fri 2012-11-24 00:00:00
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+3h30min → Fri 2012-11-23 21:45:22
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-5s → Fri 2012-11-23 18:15:17
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11min ago → Fri 2012-11-23 18:04:22
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@1395716396 → Tue 2014-03-25 03:59:56</programlisting>
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<para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
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locally, as the timezone component is not understood (unless it happens to be <literal>UTC</literal>).</para>
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<para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
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by a full stop from the seconds component. Example:</para>
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<programlisting>2014-03-25 03:59:56.654563</programlisting>
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<para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
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invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
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timestamp is formatted as follows:</para>
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<programlisting>2 months 5 days ago</programlisting>
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<para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).</para>
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</refsect1>
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<refsect1>
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<title>Calendar Events</title>
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<para>Calendar events may be used to refer to one or more points
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in time in a single expression. They form a superset of the
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absolute timestamps explained above:</para>
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<programlisting>Thu,Fri 2012-*-1,5 11:12:13</programlisting>
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<para>The above refers to 11:12:13 of the first or fifth day of
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any month of the year 2012, but only if that day is a Thursday or
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Friday.</para>
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<para>The weekday specification is optional. If specified, it
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should consist of one or more English language weekday names,
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either in the abbreviated (Wed) or non-abbreviated (Wednesday)
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form (case does not matter), separated by commas. Specifying two
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weekdays separated by <literal>..</literal> refers to a range of
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continuous weekdays. <literal>,</literal> and <literal>..</literal>
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may be combined freely.</para>
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<para>In the date and time specifications, any component may be
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specified as <literal>*</literal> in which case any value will
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match. Alternatively, each component can be specified as a list of
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values separated by commas. Values may also be suffixed with
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<literal>/</literal> and a repetition value, which indicates that
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the value itself and the value plus all multiples of the repetition value
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are matched. Each component may also contain a range of values
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separated by <literal>..</literal>.</para>
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<para>The seconds component may contain decimal fractions both in
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the value and the repetition. All fractions are rounded to 6
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decimal places.</para>
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<para>Either time or date specification may be omitted, in which
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case the current day and 00:00:00 is implied, respectively. If the
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second component is not specified, <literal>:00</literal> is
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assumed.</para>
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<para>A timezone specification is not expected, unless it is given as the literal string <literal>UTC</literal>, or
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the local timezone, similar to the supported syntax of timestamps (see above). Non-local timezones except for UTC
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are not supported.</para>
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<para>The special expressions
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<literal>minutely</literal>,
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<literal>hourly</literal>, <literal>daily</literal>,
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<literal>monthly</literal>, <literal>weekly</literal>,
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<literal>yearly</literal>,
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<literal>quarterly</literal>,
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<literal>semiannually</literal> may be used as
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calendar events which refer to
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<literal>*-*-* *:*:00</literal>,
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<literal>*-*-* *:00:00</literal>,
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<literal>*-*-* 00:00:00</literal>,
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<literal>*-*-01 00:00:00</literal>,
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<literal>Mon *-*-* 00:00:00</literal>,
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<literal>*-01-01 00:00:00</literal>,
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<literal>*-01,04,07,10-01 00:00:00</literal> and
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<literal>*-01,07-01 00:00:00</literal>, respectively.
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</para>
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<para>Examples for valid timestamps and their
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normalized form:</para>
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<programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-* 00:00:00
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Mon,Sun 12-*-* 2,1:23 → Mon,Sun 2012-*-* 01,02:23:00
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Wed *-1 → Wed *-*-01 00:00:00
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Wed..Wed,Wed *-1 → Wed *-*-01 00:00:00
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Wed, 17:48 → Wed *-*-* 17:48:00
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Wed..Sat,Tue 12-10-15 1:2:3 → Tue..Sat 2012-10-15 01:02:03
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*-*-7 0:0:0 → *-*-07 00:00:00
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10-15 → *-10-15 00:00:00
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monday *-12-* 17:00 → Mon *-12-* 17:00:00
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Mon,Fri *-*-3,1,2 *:30:45 → Mon,Fri *-*-01,02,03 *:30:45
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12,14,13,12:20,10,30 → *-*-* 12,13,14:10,20,30:00
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12..14:10,20,30 → *-*-* 12,13,14:10,20,30:00
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mon,fri *-1/2-1,3 *:30:45 → Mon,Fri *-01/2-01,03 *:30:45
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03-05 08:05:40 → *-03-05 08:05:40
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08:05:40 → *-*-* 08:05:40
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05:40 → *-*-* 05:40:00
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Sat,Sun 12-05 08:05:40 → Sat,Sun *-12-05 08:05:40
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Sat,Sun 08:05:40 → Sat,Sun *-*-* 08:05:40
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2003-03-05 05:40 → 2003-03-05 05:40:00
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05:40:23.4200004/3.1700005 → 05:40:23.420000/3.170001
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2003-02..04-05 → 2003-02,03,04-05 00:00:00
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2003-03-05 05:40 UTC → 2003-03-05 05:40:00 UTC
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2003-03-05 → 2003-03-05 00:00:00
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03-05 → *-03-05 00:00:00
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hourly → *-*-* *:00:00
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daily → *-*-* 00:00:00
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daily UTC → *-*-* 00:00:00 UTC
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monthly → *-*-01 00:00:00
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weekly → Mon *-*-* 00:00:00
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yearly → *-01-01 00:00:00
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annually → *-01-01 00:00:00
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*:2/3 → *-*-* *:02/3:00</programlisting>
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<para>Calendar events are used by timer units, see
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<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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