man 8 usermod -e, --expiredate EXPIRE_DATE information incorrect (can't be blank, must be -1 to clear)

Dear usermod man page maintainers,

  There is an error in the description of the option for:

-e, --expiredate EXPIRE_DATE

  The man page states:

An empty EXPIRE_DATE argument will disable the expiration of the account.

  This is incorrect. The EXPIRE_DATE argument CANNOT be empty or it will take
the LOGIN as the value for the EXPIRE_DATE.

  Instead, the correct use is "-e -1" or "--expiredate -1" where "-1" (-one)
is provided as the EXPIRE_DATE value.

See, e.g.: https://stackoverflow.com/a/30769911/3422102

-- 
David C. Rankin, J.D.,P.E.