Provided by: systemd_229-4ubuntu21.31_amd64 
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.
2h 30min
All specified time values are meant to be added up. The above hence refers to 150 minutes.
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
• 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 (define 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 allows for this.
Examples for valid time span specifications:
2 h
2hours
48hr
1y 12month
55s500ms
300ms20s 5day
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 according to the locale choice of the user.
PARSING TIMESTAMPS
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 ("Wed") or non-abbreviated
("Wednesday") 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).
A timestamp is considered invalid if a weekday is specified and the date does not actually
match the specified day of the week.
When parsing, systemd will also accept a few special placeholders instead 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.
When parsing, systemd will also accept relative time specifications. A time span (see
above) that is 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, a timespan prefixed with "@" is evaluated relative to the UNIX time epoch 1st
Jan, 1970, 00:00.
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
2012-11-23 → 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
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.
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:
2 months 5 days ago
Note that any relative timestamp will also parse correctly where a timestamp is expected.
(see above)
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 also be suffixed with "/" and a repetition value, which
indicates that the value and all values plus multiples of the repetition value are
matched.
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 the current day and
00:00:00 is implied, respectively. If the second component is not specified, ":00" is
assumed.
A timezone specification is not expected, unless it is given as the literal string "UTC",
similarly to timestamps.
The special expressions "minutely", "hourly", "daily", "monthly", "weekly", "yearly",
"quarterly", "semiannually" may be used as calendar events which refer to "*-*-* *:*:00",
"*-*-* *:00:00", "*-*-* 00:00:00", "*-*-01 00:00:00", "Mon *-*-* 00:00:00",
"*-01-01 00:00:00", "*-01,04,07,10-01 00:00:00" and "*-01,07-01 00:00:00", respectively.
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
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
2003-03-05 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
Calendar events are used by timer units, see systemd.timer(5) for details.
SEE ALSO
systemd(1), journalctl(1), systemd.timer(5), systemd.unit(5), systemd.directives(7)