For Rails apps running on Heroku, by default Time.now and some_time.localtime will display in UTC. If you’d like to assign a timezone to your app, you can set the TZ config variable to a time zone (which must be in the tz database timezone format).
Personally I despise the tz database format, because it requires you to guess WHICH city is chosen to represent that time zone (for Pacific, it’s Los_Angeles, not Seattle, not San_Francisco). But that’s what Heroku uses, so to set your app to Pacific you simply run:
heroku config:add TZ="America/Los_Angeles"
The allowed options are listed on the page linked above.