date should return error status on unparseable date

[dfandrich]

This invocation should return an error status and not the But it failed! message, but that's not what it does (on 0.0.17 on Alpine x86_64):

~ # uutils-date -d foo && echo But it failed!
uutils-date: invalid date 'foo'
But it failed!

date should return an error status when the -d string can't be parsed, just like GNU coreutils, Busybox, FreeBSD and Solaris already do.

[tertsdiepraam]

Thanks! Seems like we were returning 1 in a lot of other cases, but missed this one :)