To enable UTF-8 globally by default, update the default login class by adding at the end this lines in file /etc/login.conf:

   :charset=UTF-8:\
   :lang=en_US.UTF-8:

Normally add them after :umask=022::

-       :umask=022:
+       :umask=022:\
+       :charset=UTF-8:\
+       :lang=en_US.UTF-8:

After modifying /etc/login.conf run:

cap_mkdb /etc/login.conf

This will rebuild the login class capabilities database.

🔗~/.login_conf

Users may individually create a file called .login_conf in their home directory using the same format, consisting of a single entry with a record id of me.

$ cat ~/.login_conf
me:\
        :charset=UTF-8:\
        :lang=en_US.UTF-8:\
        :setenv=LC_COLLATE=C:

🔗locale

Type locale to verity that the new settings took effect:

# locale
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_ALL=