Postgres 12 - enable en_NZ.UTF-8

Hi All,

How do I enable "en_NZ.UTF-8", in Postgres 12, in the file /etc/postgresql/12/main/postgresql.conf  
Changing 'en_US.UTF-8' to 'en_NZ.UTF-8' for the following: lc_messages, lc_monetary, lc_numeric, lc_time.

And restarting Postgres 12 - I get the error "invalid value for parameter "lc_time": "en_NZ.UTF-8".

Looking at pg_collation 'en_NZ.UTF-8' does not exist.

Thanks