The RRdtool software offers a wide range of time formats. See the excerpt of the RRDtool documentation below. RRDTool_API supports these formats as well, with some differences:
- m = abbreviation, will be changed to minute
- M = abbreviation, will be changed to Month
- 0 (single character) is equal to 00 is equal to 00:00 today.
- YYYY-MM-DD is the same as DD.MM.YYYY is the same as MM/DD/YYYY
- Additionally: last = timestamp of the last stored entry.
- Additionally: first = timestamp of the first stored entry in top archive rra[0].
In case of a graph the very last respectively very first timestamp of all included databases is taken.
Specifications in the browser command line:
- e = <end time>, default: now
- l = <length of the time interval>, default: 1day
- s = <start time>, default: <end time> - <length>
- r = <resolution>, rrdfetch+select: parameter --resolution, rrdgraph: parameter --step, default: highest resolution
Parameter hierarchy:
- input value
- value from graph definition file
- default value
Start and end times:
- midnight = midnight today = midnight of the current day
- midnight -1day = midnight of the previous day
- midnight Monday = if Monday is the current day: midnight of the current day, otherwise midnight of the next Monday
- midnight Monday -1week = if Monday is the current day: midnight of Monday previous week, otherwise midnight of Monday in current week
- midnight Feb1 = midnight of February 1 in current year
- midnight Feb1 -1year = midnight of February 1 in previous year
- midnight Feb1 2022 = midnight of February 1 in year 2022
Time intervals:
- s=midnight -1day and e=midnight = complete previous day
- s=midnight Mon -1week and e=midnight Mon = complete week, maybe previous week or this week
- s=midnight Feb1 and e=midnight Mar1 = complete February this year
- s=midnight Jan1 -1year and e=midnight Jan1 = complete previous year
The function midnight() provides a comfortable method to define the start point of a day/ week/ month/ year depending on any timestamp.
Definition:
midnight(<kind of interval>, <timestamp>)
with:
- <kind of interval>: D=day|W=week|M=month|Y=year
- <timestamp>: now|last|any timestamp
First day of the week is day #1 = Monday, according to ISO 8601.
Examples:
midnight(D, now): midnight of current day (= 0 = midnight = midnight today)
midnight(D, now)-1day: midnight of previous day (= midnight today -1day)
midnight(D, last): midnight of the day with last value stored
midnight(W, now): first day of current week midnight
midnight(W, now)-1week: first day of previous week midnight
midnight(W, last): midnight of the first day of the week with last value stored
midnight(M, now): first day of current month midnight
midnight(M, now)-1Month: first day of previous month midnight
midnight(M, last): midnight of the first day of the month with last value stored
midnight(Y, now): first day of current year midnight
midnight(Y, now)-1year: first day of previous year midnight
midnight(Y, last): midnight of the first day of the year with last value stored
Source: https://oss.oetiker.ch/rrdtool/doc/rrdfetch.en.html
- --start|-s start (default end-1day)
start of the time series. A time in seconds since epoch (1970-01-01) is required. Negative numbers are relative to the current time. By default, one day worth of data will be fetched. See also AT-STYLE TIME SPECIFICATION for a detailed explanation on ways to specify the start time.
- --end|-e end (default now)
the end of the time series in seconds since epoch. See also AT-STYLE TIME SPECIFICATION for a detailed explanation of how to specify the end time.
Apart from the traditional Seconds since epoch, RRDtool does also understand at-style time specification. The specification is called "at-style" after the Unix command at(1) that has moderately complex ways to specify time to run your job at a certain date and time. The at-style specification consists of two parts: the TIME REFERENCE SPECIFICATION and the TIME OFFSET SPECIFICATION.
The time reference specification is used, well, to establish a reference moment in time (to which the time offset is then applied to). When present, it should come first, when omitted, it defaults to now. On its own part, time reference consists of a time-of-day reference (which should come first, if present) and a day reference.
The time-of-day can be specified as HH:MM, HH.MM, or just HH. You can suffix it with am or pm or use 24-hours clock. Some special times of day are understood as well, including midnight (00:00), noon (12:00) and British teatime (16:00).
The day can be specified as month-name day-of-the-month and optional a 2- or 4-digit year number (e.g. March 8 1999). Alternatively, you can use day-of-week-name (e.g. Monday), or one of the words: yesterday, today, tomorrow. You can also specify the day as a full date in several numerical formats, including MM/DD/[YY]YY, DD.MM.[YY]YY, or YYYYMMDD.
NOTE1:
this is different from the original at(1) behavior, where a single-number
date is interpreted as MMDD[YY]YY.
NOTE2:
if you specify the day in this way, the time-of-day is REQUIRED as well.
Finally, you can use the words now, start, end or epoch as your time reference. Now refers to the current moment (and is also the default time reference). Start (end) can be used to specify a time relative to the start (end) time for those tools that use these categories (rrdfetch, rrdgraph) and epoch indicates the *IX epoch (*IX timestamp 0 = 1970-01-01 00:00:00 UTC). epoch is useful to disambiguate between a timestamp value and some forms of abbreviated date/time specifications, because it allows one to use time offset specifications using units, eg. epoch+19711205s unambiguously denotes timestamp 19711205 and not 1971-12-05 00:00:00 UTC.
Month and day of the week names can be used in their naturally abbreviated form (e.g., Dec for December, Sun for Sunday, etc.). The words now, start, end can be abbreviated as n, s, e.
The time offset specification is used to add/subtract certain time intervals to/from the time reference moment. It consists of a sign (+ or -) and an amount. The following time units can be used to specify the amount: years, months, weeks, days, hours, minutes, or seconds. These units can be used in singular or plural form, and abbreviated naturally or to a single letter (e.g. +3days, -1wk, -3y). Several time units can be combined (e.g., -5mon1w2d) or concatenated (e.g., -5h45min = -5h-45min = -6h+15min = -7h+1h30m-15min, etc.)
NOTE3:
If you specify time offset in days, weeks, months, or years, you will
end with the time offset that may vary depending on your time reference,
because all those time units have no single well defined time interval value
(1 year contains either 365 or 366 days, 1 month is 28 to 31 days long, and
even 1 day may be not equal to 24 hours twice a year, when DST-related clock
adjustments take place). To cope with this, when you use days, weeks, months,
or years as your time offset units your time reference date is adjusted
accordingly without too much further effort to ensure anything about it
(in the hope that mktime(3) will take care of this later). This may lead to
some surprising (or even invalid!) results, e.g. 'May 31 -1month' = 'Apr 31'
(meaningless) = 'May 1' (after mktime(3) normalization); in the EET timezone
'3:30am Mar 29 1999 -1 day' yields '3:30am Mar 28 1999' (Sunday) which is an
invalid time/date combination (because of 3am -> 4am DST forward clock
adjustment, see the below example).
In contrast, hours, minutes, and seconds are well defined time intervals, and these are guaranteed to always produce time offsets exactly as specified (e.g. for EET timezone, '8:00 Mar 27 1999 +2 days' = '8:00 Mar 29 1999', but since there is 1-hour DST forward clock adjustment that occurs around 3:00 Mar 28 1999, the actual time interval between 8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours; on the other hand, '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999', as expected)
NOTE4:
The single-letter abbreviation for both months and minutes is m.
To disambiguate them, the parser tries to read your mind :) by applying the
following two heuristics:
-
If m is used in context of (i.e. right after the) years, months, weeks, or days it is assumed to mean months, while in the context of hours, minutes, and seconds it means minutes. (e.g., in -1y6m or +3w1m m is interpreted as months, while in -3h20m or +5s2m m the parser decides for minutes). -
Out of context (i.e. right after the + or - sign) the meaning of m is guessed from the number it directly follows. Currently, if the number's absolute value is below 6 it is assumed that m means months, otherwise it is treated as minutes. (e.g., -6m == -6m minutes, while +5m == +5 months)
Final NOTES:
- Time specification is case-insensitive.
- Whitespace can be inserted freely or omitted altogether. There are, however, cases
when whitespace is required (e.g., 'midnight Thu').
In this case you should either quote the whole phrase to prevent it from being taken apart by your shell or use '_' (underscore) or ',' (comma) which also count as whitespace (e.g., midnight_Thu or midnight,Thu).
- Oct 12 -- October 12 this year
- -1month or
-1m-1M -- current time of day, only a month before (may yield surprises, see NOTE3 above). - noon yesterday-3hours -- yesterday morning; can also be specified as 9am-1day.
- 23:59 31.12.1999 -- 1 minute to the year 2000.
- 12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.
- 12am 01/01/01 -- start of the new millennium
- end-3weeks or e-3w -- 3 weeks before end time (may be used as start time specification).
- start+6hours or s+6h -- 6 hours after start time (may be used as end time specification).
- 931200300 -- 18:45 (UTC), July 5th, 1999 (yes, seconds since 1970 are valid as well).
- 19970703 12:45 -- 12:45 July 3th, 1997 (my favorite, and it has even got an ISO number (8601)).