SYSTEMD.TIME(7) systemd.time SYSTEMD.TIME(7)
NAME
systemd.time - Time and date specifications
DESCRIPTION
In systemd, timestamps, time spans, and calendar events are displayed
and may be specified in closely related syntaxes.
DISPLAYING TIME SPANS
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:
2h 30min
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.
PARSING TIME SPANS
When parsing, systemd will accept the same time span syntax. Separating
spaces may be omitted. The following time units are understood:
• usec, us, μs
• msec, ms
• seconds, second, sec, s
• minutes, minute, min, m
• hours, hour, hr, h
• days, day, d
• weeks, week, w
• months, month, M (defined as 30.44 days)
• years, year, y (defined as 365.25 days)
If no time unit is specified, generally seconds are assumed, but some
exceptions exist and are marked as such. In a few cases "ns", "nsec" 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.
Examples for valid time span specifications:
2 h
2hours
48hr
1y 12month
55s500ms
300ms20s 5day
One can use the timespan command of systemd-analyze(1) to normalise a
textual time span for testing and validation purposes.
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
systemctl(1)'s show command displays). The former typically are
suffixed with "...Sec" to indicate the default unit of seconds, the
latter are typically suffixed with "...USec" to indicate the underlying
low-level time unit, even if they both encapsulate the very same
settings.
DISPLAYING TIMESTAMPS
Timestamps refer to specific, unique points in time. On display,
systemd will format these in the local timezone as follows:
Fri 2012-11-23 23:02:15 CET
The weekday is printed in the abbreviated English language form. The
formatting is locale-independent.
In some cases timestamps are shown in the UTC timezone instead of the
local timezone, which is indicated via the "UTC" timezone specifier in
the output.
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.
PARSING TIMESTAMPS
When parsing, systemd will accept a similar syntax, but some fields can
be omitted, and the space between the date and time can be replaced
with a "T" (à la the RFC 3339[1] profile of ISO 8601); thus, in CET,
the following are all identical: "Fri 2012-11-23 23:02:15 CET", "Fri
2012-11-23T23:02:15", "2012-11-23T23:02:15 CET", "2012-11-23 23:02:15".
The timezone defaults to the current timezone if not specified
explicitly. It may be given after a space, like above, in which case it
can be: "UTC", an entry in the installed IANA timezone database ("CET",
"Asia/Tokyo", &c.; complete list obtainable with "timedatectl
list-timezones" (see timedatectl(1))), or "±05", "±0530", "±05:30",
"Z".
It may also be affixed directly to the timestamp, in which case it must
correspond to one of the formats defined in the RFC 3339[1] profile of
ISO 8601: "±05:30" or "Z". Thus, the following are also identical to
the above: "2012-11-23T23:02:15+01:00", "2012-11-23 22:02:15Z".
A timestamp can start with a field containing a weekday, which can be
in an abbreviated ("Wed") or non-abbreviated ("Wednesday") English
language form (case does not matter), regardless of the locale.
However, if a weekday is specified and doesn't match the date, the
timestamp is rejected.
If the date is omitted, it defaults to today. If the time is omitted,
it defaults to 00:00:00. Fractional seconds can be specified down to
1µs precision. The seconds field can also be omitted, defaulting to 0.
There are special tokens that can be used in place of timestamps: "now"
may be used to refer to the current time (or of the invocation of the
command that is currently executed). "today", "yesterday", and
"tomorrow" refer to 00:00:00 of the current day, the day before, or the
next day, respectively.
Relative times are also accepted: a time span (see above) prefixed with
"+" is evaluated to the current time plus the specified time span.
Correspondingly, a time span that is prefixed with "-" is evaluated to
the current time minus the specified time span. Instead of prefixing
the time span with "+" or "-", it may also be suffixed with a space and
the word "left" or "ago".
Finally, an integer prefixed with "@" is evaluated relative to the UNIX
epoch – 1970-01-01 00:00:00 UTC.
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"):
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
2012-11-23T11:12:13Z → Fri 2012-11-23 19:12:13
2012-11-23T11:12+02:00 → Fri 2012-11-23 17:12:00
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
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 "UTC").
Timestamps may also be specified with microsecond granularity. The
sub-second remainder is expected separated by a full stop from the
seconds component. Example:
2014-03-25 03:59:56.654563
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:
2 months 5 days ago
Note that a relative timestamp is also accepted where a timestamp is
expected (see above).
Use the timestamp command of systemd-analyze(1) to validate and
normalize timestamps for testing purposes.
CALENDAR EVENTS
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:
Thu,Fri 2012-*-1,5 11:12:13
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.
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 ".."
refers to a range of continuous weekdays. "," and ".." may be
combined freely.
In the date and time specifications, any component may be specified as
"*" 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 "/" 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 ".." may be used to indicate a
range of values; ranges may also be followed with "/" 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.
A date specification may use "~" to indicate the last day in a month.
For example, "*-02~03" means "the third last day in February," and "Mon
*-05~07/1" means "the last Monday in May."
The seconds component may contain decimal fractions both in the value
and the repetition. All fractions are rounded to 6 decimal places.
Either time or date specification may be omitted, in which case *-*-*
and 00:00:00 is implied, respectively. If the seconds component is not
specified, ":00" is assumed.
Timezone can be specified as the literal string "UTC", 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).
The following special expressions may be used as shorthands for longer
normalized forms:
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
Examples for valid timestamps and their normalized form:
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
Calendar events are used by timer units, see systemd.timer(5) for
details.
Use the calendar command of systemd-analyze(1) to validate and
normalize calendar time specifications for testing purposes. The tool
also calculates when a specified calendar event would occur next.
SEE ALSO
systemd(1), journalctl(1), systemd.timer(5), systemd.unit(5),
systemd.directives(7), systemd-analyze(1)
NOTES
1. RFC 3339
https://tools.ietf.org/html/rfc3339
systemd 255 SYSTEMD.TIME(7)
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