systemd/man/systemd.time.xml

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<refentry id="systemd.time">

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

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Lennart</firstname>
                                <surname>Poettering</surname>
                                <email>lennart@poettering.net</email>
                        </author>
                </authorgroup>
        </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.</para>

                <programlisting>2h 30min</programlisting>

                <para>All specified time values are meant to be added
                up. The above hence refers to 150 minutes.</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</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</para></listitem>
                        <listitem><para>years, year, y</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 allows for this.</para>

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

                <programlisting>2 h
2hours
48hr
1y 12month
55s500ms
300ms20s 5day</programlisting>
        </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 according to the locale
                choice of the user.</para>
        </refsect1>

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

                <para>When parsing systemd will accept a similar
                timestamp syntax, but excluding any timezone
                specification (this limitation might be removed
                eventually). 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, resp., 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 actually 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>,
                <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):</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 → 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
              yesterday → Fri 2012-11-22 00:00:00
               tomorrow → Fri 2012-11-24 00:00:00
               +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 printed by systemd will not
                be parsed correctly by systemd, as the timezone
                specification is not accepted, and printing timestamps
                is subject to locale settings for the weekday while
                parsing only accepts English weekday names.</para>

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

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

                <para>Note that any relative timestamp will also parse
                correctly where a timestamp is expected. (see above)</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, given that it
                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 also be suffixed with
                <literal>/</literal> and a repetition value, which
                indicates that the value and all values plus multiples
                of the repetition value are matched.</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 names may not be specified.</para>

                <para>The special expressions
                <literal>hourly</literal>, <literal>daily</literal>,
                <literal>monthly</literal> and <literal>weekly</literal>
                may be used as calendar events which refer to
                <literal>*-*-* *:00:00</literal>, <literal>*-*-*
                00:00:00</literal>, <literal>*-*-01 00:00:00</literal> and
                <literal>Mon *-*-* 00:00:00</literal>,
                respectively.</para>

                <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
 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
                2003-03-05 → 2003-03-05 00:00:00
                     03-05 → *-03-05 00:00:00
                    hourly → *-*-* *:00:00
                     daily → *-*-* 00:00:00
                   monthly → *-*-01 00:00:00
                    weekly → Mon *-*-* 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>

        </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>
                  </para>
        </refsect1>

</refentry>