--iso seems to be an undocumented equivalent to the --iso-8601 date format, that gives you YYYY-MM-DD as the default format.
You seem to have fallen on a bug in that either, 1) date string is corrupt and doesn't emit an error 2) date string is correct but fails to generate a correct result According to the man page it is fully documented in the "info" documentation. From what I can tell the more complex relative date string (4 years 11 months ago) is not supported, https://www.gnu.org/software/coreutils/manual/html_node/Relative-items-in-date-strings.html#Relative-items-in-date-strings It would be pretty awesome if one could specify "4 years 11 months 3 days 4 hours and 7 minutes ago" but that seems not possible. In your case I also tried "4 years 11 months from 2018-05" but that just failed. On Tue, May 21, 2019 at 9:17 PM Peng Yu <[email protected]> wrote: > > Seems to work fine when date specification is not quite as ambiguous > > as "2018/05". > > > > $ date --iso --date='2018-05-01 5 years ago' > > 2013-05-01 > > What is special about --iso? If I use the following date string, I get > a future time. Why? > > $ date --date='2018-05-01 4 years 11 months ago' +%Y%m > 202106 > > -- > Regards, > Peng > > -- :wq
