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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, 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 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>minutely</literal>,
    <literal>hourly</literal>, <literal>daily</literal>,
    <literal>monthly</literal>, <literal>weekly</literal>,
    <literal>yearly</literal>,
    <literal>quarterly</literal>,
    <literal>semiannually</literal> may be used as
    calendar events which refer to
    <literal>*-*-* *:*:00</literal>,
    <literal>*-*-* *:00:00</literal>,
    <literal>*-*-* 00:00:00</literal>,
    <literal>*-*-01 00:00:00</literal>,
    <literal>Mon *-*-* 00:00:00</literal>,
    <literal>*-01-01 00:00:00</literal>,
    <literal>*-01,04,07,10-01 00:00:0</literal> and
    <literal>*-01,07-01 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
        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>

  </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>
