[ydant]

Not knocking the tool, just an alternative for people who might not be aware.

GNU date almost does the same as their examples:

    date -Is -ud 'today'    --> 2024-04-12T14:04:08+00:00
    date -Is -ud 'tomorrow' --> 2024-04-13T14:04:08+00:00
    date -Is -ud '2 day'    --> 2024-04-14T14:04:08+00:00
    date -Is -ud '9 week'   --> 2024-06-14T14:04:08+00:00
    date -Is -ud '1 month'  --> 2024-05-12T14:04:08+00:00

    date -Is -ud '2024-04-10T13:31:46+04:00'     --> 2024-04-10T09:31:46+00:00
    date -Is -ud 'Wed, 14 Feb 2024 23:16:09 GMT' --> 2024-02-14T23:16:09+00:00

And if you want Z format, you can use a custom format string:

    date -ud '1 month' +'%FT%TTZ' --> 2024-05-12T14:13:22TZ

So it would be easy enough to add an alias/function to your shell configurations and just use built-in date rather than installing a new program. Assuming GNU date relative date parsing meets your needs - I don't think it's quite as flexible as some libraries, e.g. in Python.

[smartmic]

I was thinking (and trying out) exactly the same, thanks for posting! There are many reasons to reinvent the wheel, so I have no specific feelings about this one. In my case I will certainly stick with GNU date. But there is one command line tool which complements `date` in a very helpful way: https://www.fresse.org/dateutils/

[derhuerst]

I built a JavaScript library for my needs: https://github.com/derhuerst/parse-human-relative-time