Using `date --utc --date="..."` with a date specification that decrements by years that should result in epoch=0 (1969-12-31T23:59:59+00:00) produces an "invalid date" error message.
The following commands should illustrate the problem: Notice that the only difference between the starting dates is 1 second. ```sh $ date -u -d "1970-12-31T23:59:59+00:00 - 1 year" date: invalid date ‘1970-12-31T23:59:59+00:00 - 1 year’ $ date -u -d "1970-12-31T23:59:58+00:00 - 1 year" Wed Dec 31 11:59:58 PM UTC 1969 ``` The dates are only considered invalid if they fall on epoch=0: ```sh $ date -u -d "1971-12-31T23:59:59+00:00 - 2 year" date: invalid date ‘1971-12-31T23:59:59+00:00 - 2 year’ $ date -u -d "1972-12-31T23:59:59+00:00 - 3 year" date: invalid date ‘1972-12-31T23:59:59+00:00 - 3 year’ ``` Going the other direction seems to work: ```sh $ date -u -d "1969-01-01T00:00:00+00:00 + 1 year" Thu Jan 1 12:00:00 AM UTC 1970 ``` It only seems to error when decrementing by years: ```sh date -u -d "1970-01-01T00:00:01+00:00 - 1 second" Thu Jan 1 12:00:00 AM UTC 1970 ``` It only seems to error when using --utc, because the following works (my time zone is America/Chicago): ```sh $ date -d "Wed Dec 31 06:00:00 PM CST 1970 - 1 year" +%s 0 ```
