by hroptatyr

hroptatyr / dateutils

nifty command line date and time utilities; fast date calculations and conversion in the shell

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Dateutils are a bunch of tools that revolve around fiddling with dates and times on the command line with a strong focus on use cases that arise when dealing with large amounts of financial data.

Dateutils are hosted primarily on github:

Below is a short list of examples that demonstrate what dateutils can do, for full specs refer to the info and man pages. For installation instructions refer to the INSTALL file.

Dateutils commands are prefixed with a

but otherwise resemble known unix commands for reasons of intuition. The only exception being
which is analogous to the libc function of the same name.
  • strptime
    Command line version of the C function
  • dateadd
    Add durations to dates or times
  • dateconv
    Convert dates or times between calendars
  • datediff
    Compute durations between dates or times
  • dategrep
    Grep dates or times in input streams
  • dateround
    Round dates or times to "fuller" values
  • dateseq
    Generate sequences of dates or times
  • datesort
    Sort chronologically.
  • datetest
    Compare dates or times
  • datezone
    Convert date/times to timezones in bulk


I love everything explained by example to get a first impression. So here it comes.


A tool mimicking seq(1) but whose inputs are from the domain of dates rather than integers. Typically scripts use something like

$ for i in $(seq 0 9); do
    date -d "2010-01-01 +${i} days" "+%F"

which now can be shortened to

$ dateseq 2010-01-01 2010-01-10

with the additional benefit that the end date can be given directly instead of being computed from the start date and an interval in days. Also, it provides date specific features that would be a PITA to implement using the above seq(1)/date(1) approach, like skipping certain weekdays:

$ dateseq 2010-01-01 2010-01-10 --skip sat,sun

dateseq also works on times:

$ dateseq 12:00:00 5m 12:17:00

and also date-times:

$ dateseq --compute-from-last 2012-01-02T12:00:00 5m 2012-01-02T12:17:00


A tool to convert dates between different calendric systems and/or time zones. While other such tools usually focus on converting Gregorian dates to, say, the Chinese calendar, dconv aims at supporting calendric systems which are essential in financial contexts.

To convert a (Gregorian) date into the so called ymcw representation:

$ dateconv 2012-03-04 -f "%Y-%m-%c-%w"

and vice versa:

$ dateconv 2012-03-01-Sun -i "%Y-%m-%c-%a" -f '%F'

where the ymcw representation means, the

of the month in a given year. This is useful if dates are specified like, the third Thursday in May for instance.

dateconv can also be used to convert occurrences of dates, times or date-times in an input stream on the fly

$ dateconv -S -i '%b/%d %Y at %I:%M %P' <
  Remember we meet on 2012-03-03T14:30:00

and most prominently to convert between time zones:

$ dateconv --from-zone "America/Chicago" --zone "Asia/Tokyo" 2012-01-04T09:33:00

$ dateconv --zone "America/Chicago" now -f "%d %b %Y %T" => 05 Apr 2012 11:11:57


A tool to perform date comparison in the shell, it's modelled after

but with proper command line options.
$ if datetest today --gt 2010-01-01; then
    echo "yes"


A tool to perform date arithmetic (date maths) in the shell. Given a date and a list of durations this will compute new dates. Given a duration and a list of dates this will compute new dates.

$ dateadd 2010-02-02 +4d

$ dateadd 2010-02-02 +1w => 2010-02-09

$ dateadd -1d < 2001-01-04 2000-12-31

Adding durations to times:

$ dateadd 12:05:00 +10m

and even date-times:

$ dateadd 2012-03-12T12:05:00 -1d4h

If supported by the system's zoneinfo database leap-second adjusted calculations are possible. Use the unit

to denote "real" seconds:
$ dateadd '2012-06-30 23:59:30' +30rs

as opposed to:

$ dateadd '2012-06-30 23:59:30' +30s


A tool to calculate the difference between two (or more) dates. This is somewhat the converse of dadd. Outputs will be durations that, when added to the first date, give the second date.

Get the number of days between two dates:

$ datediff 2001-02-08 2001-03-02

The duration format can be controlled through the

$ datediff 2001-02-08 2001-03-09 -f "%m month and %d day"
  1 month and 1 day

datediff also accepts time stamps as input:

$ datediff 2012-03-01T12:17:00 2012-03-02T14:00:00


switch does the right thing:
$ datediff 2012-03-01T12:17:00 2012-03-02T14:00:00 -f '%dd %Ss'
  1d 6180s

compare to:

$ datediff 2012-03-01T12:17:00 2012-03-02T14:00:00 -f '%dd %Hh %Ss'
  1d 1h 2580s

If supported by the system's zoneinfo database leap-second adjusted calculations can be made. Use the format specifier

to get the elapsed time in "real" seconds:
datediff '2012-06-30 23:59:30' '2012-07-01 00:00:30' -f '%rS'


A tool to extract lines from an input stream that match certain criteria, showing either the line or the match:

$ dategrep '<2012-03-01' <
  Feb   2012-02-28
  Feb   2012-02-29  leap day


A tool to "round" dates or time stamps to a recurring point in time, like the next/previous January or the next/previous Thursday.

Round (backwards) to the first of the current month:

$ dateround '2011-08-22' -1

Find the next Monday from the current date (today is 2016-01-08):

$ dateround today Mon

Go back to last September, then round to the end of the month:

$ dateround today -- -Sep +31d

Round a stream of dates strictly to the next month's first:

$ dateround -S -n 1 <
  pay cable 2012-03-01
  pay gas   2012-03-01
  pay rent  2012-04-01
  redeem loan   2012-04-01

Round a timeseries to the next minute (i.e. the seconds part is 00) and then to the next half-past time (and convert to ISO):

$ dateround -S 0s30m -i '%d/%m/%Y %T' -f '%F %T' <
  2012-03-06 14:30:00   eventA
  2012-03-06 14:30:00   eventA
  2012-03-06 14:30:00   eventB
  2012-03-06 15:30:00   eventB

Alternatively, if you divide the day into half-hours you can round to one of those using the co-class notation:

$ dateround -S /30m -i '%d/%m/%Y %T' -f '%F %T' <
  2012-03-06 14:30:00   eventA
  2012-03-06 14:30:00   eventA
  2012-03-06 14:30:00   eventB
  2012-03-06 15:00:00   eventB

This is largely identical to the previous example except, that a full hour (being an even multiple of half-hours) is a possible rounding target.


A tool to bring the lines of a file into chronological order.

At the moment the

tool depends on
with support for fields, in particular
to select a separator and
to sort by a particular field.
$ datesort <
  2009-06-03 caev="DVCA" secu="VOD" exch="XLON" xdte="2009-06-03" nett/GBX="5.2"
  2010-11-17 caev="DVCA" secu="VOD" exch="XLON" xdte="2010-11-17" nett/GBX="2.85"
  2011-11-16 caev="DVCA" secu="VOD" exch="XLON" xdte="2011-11-16" nett/GBX="3.05"
  2012-06-06 caev="DVCA" secu="VOD" exch="XLON" xdte="2012-06-06" nett/GBX="6.47"
  2013-06-12 caev="DVCA" secu="VOD" exch="XLON" xdte="2013-06-12" nett/GBX="6.92"
  2013-11-20 caev="DVCA" secu="VOD" exch="XLON" xdte="2013-11-20" nett/GBX="3.53"


A tool to quickly inspect date/time values in different timezones. The result will be a matrix that shows every date-time value in every timezone:

$ datezone Europe/Berlin Australia/Sydney now 2014-06-30T05:00:00
  2014-01-30T17:37:13+01:00 Europe/Berlin
  2014-01-31T03:37:13+11:00 Australia/Sydney
  2014-06-30T07:00:00+02:00 Europe/Berlin
  2014-06-30T15:00:00+10:00 Australia/Sydney


tool can also be used to obtain the next or previous DST transition relative to a given date/time:
$ datezone --next Europe/Berlin Australia/Sydney 2013-02-19
  2013-03-31T02:00:00+01:00 -> 2013-03-31T03:00:00+02:00    Europe/Berlin
  2013-04-07T03:00:00+11:00 -> 2013-04-07T02:00:00+10:00    Australia/Sydney

where the left time stamp denotes the current zone offset and the right side is the zone offset after the transition. The date/time indicates the exact moment when the transition is about to take place.

In essence

is a better


A tool that brings the flexibility of

to the command line. While (at least GNU)
has support for output formats, it lacks any kind of support to read arbitrary input from the domain of dates, in particular when the input format is specifically known beforehand and only matching dates/times shall be considered.

With the

tool reading weird dates like
Mon, May-01/2000
becomes a matter of
strptime -i "%a, %b-%d/%Y" "Mon, May-01/2000"

just as you would have done in C.

Note that

actually uses the system libc's strptime routine, and for output the system's strftime routine. Input and output modifiers will therefore vary between systems.

For a portable parser/printer combination use

as described above. Its input and output format specifiers are independent of the C runtime.

Similar projects

In no particular order and without any claim to completeness:

Use the one that best fits your purpose. And in case you happen to like mine, vote: dateutils' openhub page

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