mysql 5.7 mac app my.cnf

 Mysql 5.7 from mysql 

$ /usr/local/mysql-5.7.31-macos10.14-x86_64/bin/mysql --help --verbose | grep my.cnf

                      order of preference, my.cnf, $MYSQL_TCP_PORT,

/etc/my.cnf /etc/mysql/my.cnf /usr/local/mysql/etc/my.cnf ~/.my.cnf

It works when I created /etc/my.cnf

$ cat /etc/my.cnf

[mysqld]

default_time_zone='-08:00'

Homebrew mysql

$ mysql --help --verbose | grep my.cnf

                      order of preference, my.cnf, $MYSQL_TCP_PORT,

/etc/my.cnf /etc/mysql/my.cnf /usr/local/etc/my.cnf ~/.my.cnf

/usr/local/etc/my.cnf exists