$ gem install rubocop -v 0.72.0
$ gem install rubocop-rails -v 2.2.0
$ echo 'require: rubocop-rails' > .rubocop.yml
$ echo 'Time.new(2016, 7, 8, 12, 34, 56)' > a.rb
$ rubocop --only Rails/TimeZone --auto-correct a.rb
Inspecting 1 file
C

Offenses:

a.rb:1:6: C: [Corrected] Rails/TimeZone: Do not use Time.new without zone. Use one of Time.zone.local, Time.current, Time.new.in_time_zone, Time.new.utc, Time.new.getlocal, Time.new.xmlschema, Time.new.iso8601, Time.new.jisx0301, Time.new.rfc3339, Time.new.httpdate, Time.new.to_i, Time.new.to_f instead. (https://github.com/rubocop-hq/rails-style-guide#time, http://danilenko.org/2012/7/6/rails_timezones)
Time.new(2016, 7, 8, 12, 34, 56)
     ^^^

1 file inspected, 1 offense detected, 1 offense corrected
$ cat a.rb
Time.zone.new(2016, 7, 8, 12, 34, 56)