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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

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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, M</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 syntax, but

expects no timezone specification, unless it is given as the

literal string "UTC". In this case, the time is considered in UTC,

otherwise in the local timezone. 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 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>, 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 TZ=Asia/Shanghai):</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

11:12:13.9900009 → Fri 2012-11-23 11:12:13

format_timestamp_us: Fri 2012-11-23 11:12:13.990000

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

+3h30min → Fri 2012-11-23 21:45:22

+3h30min UTC → -EINVAL

-5s → Fri 2012-11-23 18:15:17

11min ago → Fri 2012-11-23 18:04:22

11min ago UTC → -EINVAL

@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>A timezone specification is not expected, unless it is given

as the literal string "UTC", similarly to timestamps.</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 00:00:00</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 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

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>