In Rails, how get current time zone (Time.zone) in a format that can be used with ActiveSupport::TimeZone[zone].parse()?

Use Time.zone.name, not Time.zone.to_s

[1] pry(main)> Time.zone.to_s=> "(GMT-05:00) Eastern Time (US & Canada)"[2] pry(main)> Time.zone.name=> "Eastern Time (US & Canada)"[3] pry(main)> ActiveSupport::TimeZone[Time.zone.name]=> (GMT-05:00) Eastern Time (US & Canada)

As for how I got this (as requested), I just know the name method exists on Time.zone. If I didn't know this by heart though, I will check the docs. If it's not in there as you say (and it is, here), I typically inspect the class/module/object with Pry. Pry is an alternative to irb that lets me do something like

[1] pry(main)> cd Time.zone[2] pry(#<ActiveSupport::TimeZone>):1> ls -mComparable#methods: <  <=  ==  >  >=  between?ActiveSupport::TimeZone#methods: <=>  =~  at  formatted_offset  local  local_to_utc  name  now  parse  period_for_local  period_for_utc  to_s  today  tzinfo  utc_offset  utc_to_localself.methods: __pry__[3] pry(#<ActiveSupport::TimeZone>):1> name=> "Eastern Time (US & Canada)"

ls -m on line [2] above prints methods on the object (if you scroll right you'll see name listed there). You can see in [3] I can call name directly on the Time.zone object I'm inside of and get the output you're looking for.