man/systemd.time.xml - systemd - Git at Google

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 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

 <refentry id="systemd.time">

   <refentryinfo>
     <title>systemd.time</title>
     <productname>systemd</productname>
   </refentryinfo>

   <refmeta>
     <refentrytitle>systemd.time</refentrytitle>
     <manvolnum>7</manvolnum>
   </refmeta>

   <refnamediv>
     <refname>systemd.time</refname>
     <refpurpose>Time and date specifications</refpurpose>
   </refnamediv>

   <refsect1>
     <title>Description</title>

     <para>In systemd, timestamps, time spans, and calendar events are
     displayed and may be specified in closely related syntaxes.</para>
   </refsect1>

   <refsect1>
     <title>Displaying Time Spans</title>

     <para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
     of time values each suffixed by a time unit. Example:</para>

     <programlisting>2h 30min</programlisting>

     <para>All specified time values are meant to be added up. The above hence refers to 150 minutes. Display is
     locale-independent, only English names for the time units are used.</para>
   </refsect1>

   <refsect1>
     <title>Parsing Time Spans</title>

     <para>When parsing, systemd will accept the same time span syntax.
     Separating spaces may be omitted. The following time units are
     understood:</para>

     <itemizedlist>
       <listitem><para>usec, us, µs</para></listitem>
       <listitem><para>msec, ms</para></listitem>
       <listitem><para>seconds, second, sec, s</para></listitem>
       <listitem><para>minutes, minute, min, m</para></listitem>
       <listitem><para>hours, hour, hr, h</para></listitem>
       <listitem><para>days, day, d</para></listitem>
       <listitem><para>weeks, week, w</para></listitem>
       <listitem><para>months, month, M (defined as 30.44 days)</para></listitem>
       <listitem><para>years, year, y (defined as 365.25 days)</para></listitem>
     </itemizedlist>

     <para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
     such. In a few cases <literal>ns</literal>, <literal>nsec</literal> is accepted too, where the granularity of the
     time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
     accepted.</para>

     <para>Examples for valid time span specifications:</para>

     <programlisting>2 h
 2hours
 48hr
 1y 12month
 55s500ms
 300ms20s 5day</programlisting>

     <para>One can use the <command>timespan</command> command of
     <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
     to normalise a textual time span for testing and validation purposes.</para>

     <para>Internally, systemd generally operates with microsecond time granularity, while the default time
     unit in user-configurable time spans is usually seconds (see above). This disparity becomes visible when
     comparing the same settings in the (high-level) unit file syntax with the matching (more low-level) D-Bus
     properties (which are what
     <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
     <command>show</command> command displays). The former typically are suffixed with <literal>…Sec</literal>
     to indicate the default unit of seconds, the latter are typically suffixed with <literal>…USec</literal>
     to indicate the underlying low-level time unit, even if they both encapsulate the very same
     settings.</para>
   </refsect1>

   <refsect1>
     <title>Displaying Timestamps</title>

     <para>Timestamps refer to specific, unique points in time. On
     display, systemd will format these in the local timezone as
     follows:</para>

     <programlisting>Fri 2012-11-23 23:02:15 CET</programlisting>

     <para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.</para>

     <para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
     the <literal>UTC</literal> timezone specifier in the output.</para>

     <para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
     separated by a full stop from the seconds component.</para>
   </refsect1>

   <refsect1>
     <title>Parsing Timestamps</title>

     <para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless
     it is given as the literal string <literal>UTC</literal> (for the UTC timezone), or is specified to be
     the locally configured timezone, or the timezone name in the IANA timezone database format. The complete
     list of timezones supported on your system can be obtained using the <literal>timedatectl
     list-timezones</literal> (see
     <citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>).  Using
     IANA format is recommended over local timezone names, as less prone to errors (e.g. with local timezone
     it's possible to specify daylight saving time in winter, even though that is not correct). The weekday
     specification is optional, but when the weekday is specified, it must either be in the abbreviated
     (<literal>Wed</literal>) or non-abbreviated (<literal>Wednesday</literal>) English language form (case
     does not matter), and is not subject to the locale choice of the user. Either the date, or the time part
     may be omitted, in which case the current date or 00:00:00, respectively, is assumed. The seconds
     component of the time may also be omitted, in which case ":00" is assumed. Year numbers may be specified
     in full or may be abbreviated (omitting the century).</para>

     <para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
     the week.</para>

     <para>When parsing, systemd will also accept a few special
     placeholders instead of timestamps: <literal>now</literal> may be
     used to refer to the current time (or of the invocation of the
     command that is currently executed). <literal>today</literal>,
     <literal>yesterday</literal>, and <literal>tomorrow</literal> refer to
     00:00:00 of the current day, the day before, or the next day,
     respectively.</para>

     <para>When parsing, systemd will also accept relative time
     specifications. A time span (see above) that is prefixed with
     <literal>+</literal> is evaluated to the current time plus the
     specified time span. Correspondingly, a time span that is prefixed
     with <literal>-</literal> is evaluated to the current time minus
     the specified time span. Instead of prefixing the time span with
     <literal>+</literal> or <literal>-</literal>, it may also be
     suffixed with a space and the word <literal>left</literal> or
     <literal>ago</literal>.</para>

     <para>Finally, a timespan prefixed with <literal>@</literal> is
     evaluated relative to the UNIX time epoch 1st Jan, 1970,
     00:00.</para>

     <para>Examples for valid timestamps and their normalized form (assuming the current time was 2012-11-23
     18:15:22 and the timezone was UTC+8, for example <literal>TZ=:Asia/Shanghai</literal>):</para>

     <programlisting>  Fri 2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
       2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
   2012-11-23 11:12:13 UTC → Fri 2012-11-23 19:12:13
                2012-11-23 → Fri 2012-11-23 00:00:00
                  12-11-23 → Fri 2012-11-23 00:00:00
                  11:12:13 → Fri 2012-11-23 11:12:13
                     11:12 → Fri 2012-11-23 11:12:00
                       now → Fri 2012-11-23 18:15:22
                     today → Fri 2012-11-23 00:00:00
                 today UTC → Fri 2012-11-23 16:00:00
                 yesterday → Fri 2012-11-22 00:00:00
                  tomorrow → Fri 2012-11-24 00:00:00
 tomorrow Pacific/Auckland → Thu 2012-11-23 19:00:00
                  +3h30min → Fri 2012-11-23 21:45:22
                       -5s → Fri 2012-11-23 18:15:17
                 11min ago → Fri 2012-11-23 18:04:22
               @1395716396 → Tue 2014-03-25 03:59:56</programlisting>

     <para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
     locally, as the timezone component is not understood (unless it happens to be <literal>UTC</literal>).</para>

     <para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
     by a full stop from the seconds component. Example:</para>

     <programlisting>2014-03-25 03:59:56.654563</programlisting>

     <para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
     invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
     timestamp is formatted as follows:</para>

     <programlisting>2 months 5 days ago</programlisting>

     <para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).</para>

     <para>Use the <command>timestamp</command> command of
     <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
     validate and normalize timestamps for testing purposes.</para>
   </refsect1>

   <refsect1>
     <title>Calendar Events</title>

     <para>Calendar events may be used to refer to one or more points
     in time in a single expression. They form a superset of the
     absolute timestamps explained above:</para>

     <programlisting>Thu,Fri 2012-*-1,5 11:12:13</programlisting>

     <para>The above refers to 11:12:13 of the first or fifth day of
     any month of the year 2012, but only if that day is a Thursday or
     Friday.</para>

     <para>The weekday specification is optional. If specified, it
     should consist of one or more English language weekday names,
     either in the abbreviated (Wed) or non-abbreviated (Wednesday)
     form (case does not matter), separated by commas. Specifying two
     weekdays separated by <literal>..</literal> refers to a range of
     continuous weekdays. <literal>,</literal> and <literal>..</literal>
     may be combined freely.</para>

     <para>In the date and time specifications, any component may be specified as <literal>*</literal> in
     which case any value will match. Alternatively, each component can be specified as a list of values
     separated by commas. Values may be suffixed with <literal>/</literal> and a repetition value, which
     indicates that the value itself and the value plus all multiples of the repetition value are matched.
     Two values separated by <literal>..</literal> may be used to indicate a range of values; ranges may also
     be followed with <literal>/</literal> and a repetition value, in which case the expression matches all
     times starting with the start value, and continuing with all multiples of the repetition value relative
     to the start value, ending at the end value the latest.</para>

     <para>A date specification may use <literal>~</literal> to indicate the
     last day(s) in a month. For example, <literal>*-02~03</literal> means
     "the third last day in February," and <literal>Mon *-05~07/1</literal>
     means "the last Monday in May."</para>

     <para>The seconds component may contain decimal fractions both in
     the value and the repetition. All fractions are rounded to 6
     decimal places.</para>

     <para>Either time or date specification may be omitted, in which
     case the current day and 00:00:00 is implied, respectively. If the
     second component is not specified, <literal>:00</literal> is
     assumed.</para>

     <para>Timezone can be specified as the literal string <literal>UTC</literal>, or
     the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
     in the IANA timezone database format (also see above).</para>

   <para>The following special expressions may be used as shorthands for longer normalized forms:</para>

     <programlisting>    minutely → *-*-* *:*:00
       hourly → *-*-* *:00:00
        daily → *-*-* 00:00:00
      monthly → *-*-01 00:00:00
       weekly → Mon *-*-* 00:00:00
       yearly → *-01-01 00:00:00
    quarterly → *-01,04,07,10-01 00:00:00
 semiannually → *-01,07-01 00:00:00
    </programlisting>

     <para>Examples for valid timestamps and their
     normalized form:</para>

 <programlisting>  Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun *-*-* 00:00:00
       Mon,Sun 12-*-* 2,1:23 → Mon,Sun 2012-*-* 01,02:23:00
                     Wed *-1 → Wed *-*-01 00:00:00
            Wed..Wed,Wed *-1 → Wed *-*-01 00:00:00
                  Wed, 17:48 → Wed *-*-* 17:48:00
 Wed..Sat,Tue 12-10-15 1:2:3 → Tue..Sat 2012-10-15 01:02:03
                 *-*-7 0:0:0 → *-*-07 00:00:00
                       10-15 → *-10-15 00:00:00
         monday *-12-* 17:00 → Mon *-12-* 17:00:00
   Mon,Fri *-*-3,1,2 *:30:45 → Mon,Fri *-*-01,02,03 *:30:45
        12,14,13,12:20,10,30 → *-*-* 12,13,14:10,20,30:00
             12..14:10,20,30 → *-*-* 12..14:10,20,30:00
   mon,fri *-1/2-1,3 *:30:45 → Mon,Fri *-01/2-01,03 *:30:45
              03-05 08:05:40 → *-03-05 08:05:40
                    08:05:40 → *-*-* 08:05:40
                       05:40 → *-*-* 05:40:00
      Sat,Sun 12-05 08:05:40 → Sat,Sun *-12-05 08:05:40
            Sat,Sun 08:05:40 → Sat,Sun *-*-* 08:05:40
            2003-03-05 05:40 → 2003-03-05 05:40:00
  05:40:23.4200004/3.1700005 → *-*-* 05:40:23.420000/3.170001
              2003-02..04-05 → 2003-02..04-05 00:00:00
        2003-03-05 05:40 UTC → 2003-03-05 05:40:00 UTC
                  2003-03-05 → 2003-03-05 00:00:00
                       03-05 → *-03-05 00:00:00
                      hourly → *-*-* *:00:00
                       daily → *-*-* 00:00:00
                   daily UTC → *-*-* 00:00:00 UTC
                     monthly → *-*-01 00:00:00
                      weekly → Mon *-*-* 00:00:00
     weekly Pacific/Auckland → Mon *-*-* 00:00:00 Pacific/Auckland
                      yearly → *-01-01 00:00:00
                    annually → *-01-01 00:00:00
                       *:2/3 → *-*-* *:02/3:00</programlisting>

       <para>Calendar events are used by timer units, see
       <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
       for details.</para>

       <para>Use the <command>calendar</command> command of
       <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
       and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
       calendar event would occur next.</para>
   </refsect1>

   <refsect1>
       <title>See Also</title>
       <para>
         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
         <citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
         <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
       </para>
   </refsect1>

 </refentry>
	<?xml version='1.0'?> <!---nxml--->
	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
	<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

	<refentry id="systemd.time">

	<refentryinfo>
	<title>systemd.time</title>
	<productname>systemd</productname>
	</refentryinfo>

	<refmeta>
	<refentrytitle>systemd.time</refentrytitle>
	<manvolnum>7</manvolnum>
	</refmeta>

	<refnamediv>
	<refname>systemd.time</refname>
	<refpurpose>Time and date specifications</refpurpose>
	</refnamediv>

	<refsect1>
	<title>Description</title>

	<para>In systemd, timestamps, time spans, and calendar events are
	displayed and may be specified in closely related syntaxes.</para>
	</refsect1>

	<refsect1>
	<title>Displaying Time Spans</title>

	<para>Time spans refer to time durations. On display, systemd will present time spans as a space-separated series
	of time values each suffixed by a time unit. Example:</para>

	<programlisting>2h 30min</programlisting>

	<para>All specified time values are meant to be added up. The above hence refers to 150 minutes. Display is
	locale-independent, only English names for the time units are used.</para>
	</refsect1>

	<refsect1>
	<title>Parsing Time Spans</title>

	<para>When parsing, systemd will accept the same time span syntax.
	Separating spaces may be omitted. The following time units are
	understood:</para>

	<itemizedlist>
	<listitem><para>usec, us, µs</para></listitem>
	<listitem><para>msec, ms</para></listitem>
	<listitem><para>seconds, second, sec, s</para></listitem>
	<listitem><para>minutes, minute, min, m</para></listitem>
	<listitem><para>hours, hour, hr, h</para></listitem>
	<listitem><para>days, day, d</para></listitem>
	<listitem><para>weeks, week, w</para></listitem>
	<listitem><para>months, month, M (defined as 30.44 days)</para></listitem>
	<listitem><para>years, year, y (defined as 365.25 days)</para></listitem>
	</itemizedlist>

	<para>If no time unit is specified, generally seconds are assumed, but some exceptions exist and are marked as
	such. In a few cases <literal>ns</literal>, <literal>nsec</literal> is accepted too, where the granularity of the
	time span permits this. Parsing is generally locale-independent, non-English names for the time units are not
	accepted.</para>

	<para>Examples for valid time span specifications:</para>

	<programlisting>2 h
	2hours
	48hr
	1y 12month
	55s500ms
	300ms20s 5day</programlisting>

	<para>One can use the <command>timespan</command> command of
	<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
	to normalise a textual time span for testing and validation purposes.</para>

	<para>Internally, systemd generally operates with microsecond time granularity, while the default time
	unit in user-configurable time spans is usually seconds (see above). This disparity becomes visible when
	comparing the same settings in the (high-level) unit file syntax with the matching (more low-level) D-Bus
	properties (which are what
	<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
	<command>show</command> command displays). The former typically are suffixed with <literal>…Sec</literal>
	to indicate the default unit of seconds, the latter are typically suffixed with <literal>…USec</literal>
	to indicate the underlying low-level time unit, even if they both encapsulate the very same
	settings.</para>
	</refsect1>

	<refsect1>
	<title>Displaying Timestamps</title>

	<para>Timestamps refer to specific, unique points in time. On
	display, systemd will format these in the local timezone as
	follows:</para>

	<programlisting>Fri 2012-11-23 23:02:15 CET</programlisting>

	<para>The weekday is printed in the abbreviated English language form. The formatting is locale-independent.</para>

	<para>In some cases timestamps are shown in the UTC timezone instead of the local timezone, which is indicated via
	the <literal>UTC</literal> timezone specifier in the output.</para>

	<para>In some cases timestamps are shown with microsecond granularity. In this case the sub-second remainder is
	separated by a full stop from the seconds component.</para>
	</refsect1>

	<refsect1>
	<title>Parsing Timestamps</title>

	<para>When parsing, systemd will accept a similar syntax, but expects no timezone specification, unless
	it is given as the literal string <literal>UTC</literal> (for the UTC timezone), or is specified to be
	the locally configured timezone, or the timezone name in the IANA timezone database format. The complete
	list of timezones supported on your system can be obtained using the <literal>timedatectl
	list-timezones</literal> (see
	<citerefentry><refentrytitle>timedatectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Using
	IANA format is recommended over local timezone names, as less prone to errors (e.g. with local timezone
	it's possible to specify daylight saving time in winter, even though that is not correct). The weekday
	specification is optional, but when the weekday is specified, it must either be in the abbreviated
	(<literal>Wed</literal>) or non-abbreviated (<literal>Wednesday</literal>) English language form (case
	does not matter), and is not subject to the locale choice of the user. Either the date, or the time part
	may be omitted, in which case the current date or 00:00:00, respectively, is assumed. The seconds
	component of the time may also be omitted, in which case ":00" is assumed. Year numbers may be specified
	in full or may be abbreviated (omitting the century).</para>

	<para>A timestamp is considered invalid if a weekday is specified and the date does not match the specified day of
	the week.</para>

	<para>When parsing, systemd will also accept a few special
	placeholders instead of timestamps: <literal>now</literal> may be
	used to refer to the current time (or of the invocation of the
	command that is currently executed). <literal>today</literal>,
	<literal>yesterday</literal>, and <literal>tomorrow</literal> refer to
	00:00:00 of the current day, the day before, or the next day,
	respectively.</para>

	<para>When parsing, systemd will also accept relative time
	specifications. A time span (see above) that is prefixed with
	<literal>+</literal> is evaluated to the current time plus the
	specified time span. Correspondingly, a time span that is prefixed
	with <literal>-</literal> is evaluated to the current time minus
	the specified time span. Instead of prefixing the time span with
	<literal>+</literal> or <literal>-</literal>, it may also be
	suffixed with a space and the word <literal>left</literal> or
	<literal>ago</literal>.</para>

	<para>Finally, a timespan prefixed with <literal>@</literal> is
	evaluated relative to the UNIX time epoch 1st Jan, 1970,
	00:00.</para>

	<para>Examples for valid timestamps and their normalized form (assuming the current time was 2012-11-23
	18:15:22 and the timezone was UTC+8, for example <literal>TZ=:Asia/Shanghai</literal>):</para>

	<programlisting> Fri 2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
	2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
	2012-11-23 11:12:13 UTC → Fri 2012-11-23 19:12:13
	2012-11-23 → Fri 2012-11-23 00:00:00
	12-11-23 → Fri 2012-11-23 00:00:00
	11:12:13 → Fri 2012-11-23 11:12:13
	11:12 → Fri 2012-11-23 11:12:00
	now → Fri 2012-11-23 18:15:22
	today → Fri 2012-11-23 00:00:00
	today UTC → Fri 2012-11-23 16:00:00
	yesterday → Fri 2012-11-22 00:00:00
	tomorrow → Fri 2012-11-24 00:00:00
	tomorrow Pacific/Auckland → Thu 2012-11-23 19:00:00
	+3h30min → Fri 2012-11-23 21:45:22
	-5s → Fri 2012-11-23 18:15:17
	11min ago → Fri 2012-11-23 18:04:22
	@1395716396 → Tue 2014-03-25 03:59:56</programlisting>

	<para>Note that timestamps displayed by remote systems with a non-matching timezone are usually not parsable
	locally, as the timezone component is not understood (unless it happens to be <literal>UTC</literal>).</para>

	<para>Timestamps may also be specified with microsecond granularity. The sub-second remainder is expected separated
	by a full stop from the seconds component. Example:</para>

	<programlisting>2014-03-25 03:59:56.654563</programlisting>

	<para>In some cases, systemd will display a relative timestamp (relative to the current time, or the time of
	invocation of the command) instead of or in addition to an absolute timestamp as described above. A relative
	timestamp is formatted as follows:</para>

	<programlisting>2 months 5 days ago</programlisting>

	<para>Note that a relative timestamp is also accepted where a timestamp is expected (see above).</para>

	<para>Use the <command>timestamp</command> command of
	<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry> to
	validate and normalize timestamps for testing purposes.</para>
	</refsect1>

	<refsect1>
	<title>Calendar Events</title>

	<para>Calendar events may be used to refer to one or more points
	in time in a single expression. They form a superset of the
	absolute timestamps explained above:</para>

	<programlisting>Thu,Fri 2012-*-1,5 11:12:13</programlisting>

	<para>The above refers to 11:12:13 of the first or fifth day of
	any month of the year 2012, but only if that day is a Thursday or
	Friday.</para>

	<para>The weekday specification is optional. If specified, it
	should consist of one or more English language weekday names,
	either in the abbreviated (Wed) or non-abbreviated (Wednesday)
	form (case does not matter), separated by commas. Specifying two
	weekdays separated by <literal>..</literal> refers to a range of
	continuous weekdays. <literal>,</literal> and <literal>..</literal>
	may be combined freely.</para>

	<para>In the date and time specifications, any component may be specified as <literal>*</literal> in
	which case any value will match. Alternatively, each component can be specified as a list of values
	separated by commas. Values may be suffixed with <literal>/</literal> and a repetition value, which
	indicates that the value itself and the value plus all multiples of the repetition value are matched.
	Two values separated by <literal>..</literal> may be used to indicate a range of values; ranges may also
	be followed with <literal>/</literal> and a repetition value, in which case the expression matches all
	times starting with the start value, and continuing with all multiples of the repetition value relative
	to the start value, ending at the end value the latest.</para>

	<para>A date specification may use <literal>~</literal> to indicate the
	last day(s) in a month. For example, <literal>*-02~03</literal> means
	"the third last day in February," and <literal>Mon *-05~07/1</literal>
	means "the last Monday in May."</para>

	<para>The seconds component may contain decimal fractions both in
	the value and the repetition. All fractions are rounded to 6
	decimal places.</para>

	<para>Either time or date specification may be omitted, in which
	case the current day and 00:00:00 is implied, respectively. If the
	second component is not specified, <literal>:00</literal> is
	assumed.</para>

	<para>Timezone can be specified as the literal string <literal>UTC</literal>, or
	the local timezone, similar to the supported syntax of timestamps (see above), or the timezone
	in the IANA timezone database format (also see above).</para>

	<para>The following special expressions may be used as shorthands for longer normalized forms:</para>

	<programlisting> minutely → --* ::00
	hourly → --* *:00:00
	daily → --* 00:00:00
	monthly → --01 00:00:00
	weekly → Mon --* 00:00:00
	yearly → *-01-01 00:00:00
	quarterly → *-01,04,07,10-01 00:00:00
	semiannually → *-01,07-01 00:00:00
	</programlisting>

	<para>Examples for valid timestamps and their
	normalized form:</para>

	<programlisting> Sat,Thu,Mon..Wed,Sat..Sun → Mon..Thu,Sat,Sun --* 00:00:00
	Mon,Sun 12-- 2,1:23 → Mon,Sun 2012-- 01,02:23:00
	Wed -1 → Wed -*-01 00:00:00
	Wed..Wed,Wed -1 → Wed -*-01 00:00:00
	Wed, 17:48 → Wed --* 17:48:00
	Wed..Sat,Tue 12-10-15 1:2:3 → Tue..Sat 2012-10-15 01:02:03
	--7 0:0:0 → --07 00:00:00
	10-15 → *-10-15 00:00:00
	monday -12- 17:00 → Mon -12- 17:00:00
	Mon,Fri --3,1,2 :30:45 → Mon,Fri --01,02,03 :30:45
	12,14,13,12:20,10,30 → --* 12,13,14:10,20,30:00
	12..14:10,20,30 → --* 12..14:10,20,30:00
	mon,fri -1/2-1,3 :30:45 → Mon,Fri -01/2-01,03 :30:45
	03-05 08:05:40 → *-03-05 08:05:40
	08:05:40 → --* 08:05:40
	05:40 → --* 05:40:00
	Sat,Sun 12-05 08:05:40 → Sat,Sun *-12-05 08:05:40
	Sat,Sun 08:05:40 → Sat,Sun --* 08:05:40
	2003-03-05 05:40 → 2003-03-05 05:40:00
	05:40:23.4200004/3.1700005 → --* 05:40:23.420000/3.170001
	2003-02..04-05 → 2003-02..04-05 00:00:00
	2003-03-05 05:40 UTC → 2003-03-05 05:40:00 UTC
	2003-03-05 → 2003-03-05 00:00:00
	03-05 → *-03-05 00:00:00
	hourly → --* *:00:00
	daily → --* 00:00:00
	daily UTC → --* 00:00:00 UTC
	monthly → --01 00:00:00
	weekly → Mon --* 00:00:00
	weekly Pacific/Auckland → Mon --* 00:00:00 Pacific/Auckland
	yearly → *-01-01 00:00:00
	annually → *-01-01 00:00:00
	:2/3 → -- *:02/3:00</programlisting>

	<para>Calendar events are used by timer units, see
	<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>
	for details.</para>

	<para>Use the <command>calendar</command> command of
	<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry> to validate
	and normalize calendar time specifications for testing purposes. The tool also calculates when a specified
	calendar event would occur next.</para>
	</refsect1>

	<refsect1>
	<title>See Also</title>
	<para>
	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd.timer</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
	</para>
	</refsect1>

	</refentry>