date: doesn't support `-d"xxx +23 day"`

[sylvestre]

example:

$ /usr/bin/date -d'2005-01-01 +351 day'
2005
$ ./target/debug/coreutils date -d'2005-01-01 +351 day'
date: invalid date '2005-01-01 +351 day'

Tested here:
https://github.com/coreutils/coreutils/blob/master/tests/date/date.pl#L325

[dhilst]

I'm working on this, I have a fallback parsing code here: #6667
I'm looking at other issues about date formatting as well

[jfinkels]

This is working with the update to parse_datetime v0.8.0:

$ date -d'2005-01-01 +351 day'
Sun Dec 18 12:00:00 AM EST 2005
$ ./target/debug/date -d'2005-01-01 +351 day'
Sun Dec 18 00:00:00 EST 2005

(The format is slightly different, but the date and time are correct.)