Ruby convert UTC to local time zone

utc_to_localtime.rb

require 'Time'
utc_time_str = '2020-01-02T18:16:35+0000'

# Outputs UTC time.
Time.parse(utc_time_str)
=> 2020-01-02 18:16:35 +0000

# Outputs system timezone. Also can use to_time
Time.parse(utc_time_str).to_localtime
=> 2020-01-02 13:16:35 -0500

# With ActiveSupport you can set the current threads time zone.
# This is how RoR handles setting time zones on web requests.
require 'active_support/all'

# Start with a UTC time (say from an SQL query.
# NOTE: No time zone info in string.
utc_time_str = '2020-1-2 18:16:35'

# Parse time from SQL query declaring as UTC TZ.
utc_time = Time.find_zone('UTC').parse(utc_time_str)
=> Thu, 02 Jan 2020 18:16:35 UTC +00:00

# Set the timezone to convert to. This is done in the request in RoR. 
Time.zone = 'Central Time (US & Canada)'
Time.zone.parse(utc_time.to_s)
=> Thu, 02 Jan 2020 12:16:35 CST -06:00