Command-line Interface

For a detailed description of the command-line interface, see Command-line Interface.

Date arithmetic

The earthkit-date command provides utilities to shift and subtract dates. For instance, to get the date 13 days before a reference:

$ earthkit-date shift 20160219 -13
20160206

Positive and negative shifts are supported. To do the reverse and compute how many days there are between two dates:

$ earthkit-date diff 20241225 20240314
286

Date sequences

The earthkit-dateseq command provides various utilities to manipulate sequences of recurring dates.

Specifying a sequence

Example	Description
`--daily`	Sequence recurring every day
`--daily --exclude 31`	Sequence recurring every day, except the 31^st
`--weekly mon/thu`	Sequence recurring every Monday and Thursday
`--monthly 1/15`	Sequence recurring every 1^st and 15^th of the month
`--monthly 1/8/15/22/29 --exclude 0229`	Sequence recurring every 7 days each month, skipping the 29^th February
`--yearly 1225`	Sequence recurring every year on the 25^th December
`--preset ecmwf-4days`	Pre-defined sequence (equivalent to `--monthly 1/5/.../29 --exclude 0229`)

All the arguments can take slash-separated lists to specify multiple occurrences within a week, month, or year, as well as multiple excludes. Week days can be numeric (0 is Monday, 1 is Tuesday, etc.) or any unambiguous prefix of the name (e.g., M, sa, FRIDAY).

Computing individual dates

To get the previous or next date in a sequence, use earthkit-dateseq previous or earthkit-dateseq next:

$ earthkit-dateseq previous --weekly wed/fri 20240512
20240510
$ earthkit-dateseq next --weekly wed/fri 20240510
20240515
$ earthkit-dateseq next --weekly wed/fri --inclusive 20240510
20240510
$ earthkit-dateseq next --weekly wed/fri --skip 3 20240510
20240524

If the given date is in the sequence, the default behaviour is to skip to the previous or next one. To keep it, add the --inclusive option. More dates can be skipped with the --skip option.

Similarly, the sequence date closest to a given date can be computed using earthkit-dateseq nearest:

$ earthkit-dateseq nearest --monthly 1/15 20240704
20240701
$ earthkit-dateseq nearest --monthly 1/15 20240320
20240315
$ earthkit-dateseq nearest --monthly 1/15 20240808
20240801
$ earthkit-dateseq nearest --monthly 1/15 --resolve next 20240808
20240815

If there is a tie, meaning that the given date is equidistant from the previous and next date in the sequence, the previous date is returned. This behaviour can be explicitly controlled by passing --resolve previous or --resolve next.

Computing sets of dates

To find all the sequence dates falling within a range, use earthkit-dateseq range:

$ earthkit-dateseq range --sep ", " --weekly 0/2/4 20241201 20241216
20241202, 20241204, 20241206, 20241209, 20241211, 20241213, 20241216
$ earthkit-dateseq range --sep ", " --weekly 0/2/4 --exclude-end 20241201 20241216
20241202, 20241204, 20241206, 20241209, 20241211, 20241213
$ earthkit-dateseq range --sep ", " --weekly 0/2/4 --exclude-start 20241202 20241216
20241204, 20241206, 20241209, 20241211, 20241213, 20241216

By default, ranges include the given start and end dates. The --exclude-start and --exclude-end flags override this behaviour.

The output sequences are formatted using the value of --sep, if present, otherwise each date is printed on a separate line.

To get a given number of dates around one reference, use earthkit-dateseq bracket:

$ earthkit-dateseq bracket --sep ", " --weekly Saturday 19991127
19991120, 19991204
$ earthkit-dateseq bracket --sep ", " --weekly Saturday --inclusive 19991127
19991120, 19991127, 19991204
$ earthkit-dateseq bracket --sep ", " --weekly Saturday 20060528 3
20060513, 20060520, 20060527, 20060603, 20060610, 20060617
$ earthkit-dateseq bracket --sep ", " --weekly Saturday 20150403 1 2
20150328, 20150404, 20150411
$ earthkit-dateseq bracket --sep ", " --weekly Saturday --inclusive 19930717 2 1
19930703, 19930710, 19930717, 19930724

The last two optional arguments are the number of dates to output, respectively before and after the reference date. If none is given, one date either side is returned. If one is given, the same number of dates either side is returned. If the --inclusive flag is set and the reference date is in the sequence, it is printed as well (but not counted towards the numbers requested).

Model climate dates

The earthkit-climdates command provides utilities to create sets of dates for model climates.

To get one date per year on the same day as a given reference, use earthkit-climdates range:

$ earthkit-climdates range --sep ", " --from-year 2000 --to-year 2005 20061023
20001023, 20011023, 20021023, 20031023, 20041023, 20051023
$ earthkit-climdates range --sep ", " --from-date 20020608 --to-date 20040701 20050602
20030602, 20040602
$ earthkit-climdates range --sep ", " --from-rel-year -3 --to-rel-year -1 20100805
20070805, 20080805, 20090805

To combine yearly dates with multiple reference dates taken from a sequence, use earthkit-climdates mclim:

$ earthkit-climdates mclim --sep ", " --from-year 2018 --to-year 2020 --before 7 --after 7 --preset ecmwf-mon-thu 20230806
20180731, 20180803, 20180807, 20180810, 20190731, 20190803, 20190807, 20190810, 20200731, 20200803, 20200807, 20200810
$ earthkit-climdates mclim --sep ", " --from-rel-year -7 --to-rel-year -4 --before 5 --after 5 --preset ecmwf-mon-thu 20230101
20151229, 20160102, 20160105, 20161229, 20170102, 20170105, 20171229, 20180102, 20180105, 20181229, 20190102, 20190105