method

ago

rails latest stable - Class: ActiveSupport::Duration

ago(time = ::Time.current)

public

Calculates a new Time or Date that is as far in the past as this Duration represents.

# File activesupport/lib/active_support/duration.rb, line 439
    def ago(time = ::Time.current)
      sum(-1, time)
    end

lazylester · Jul 2, 2014

From the description of Time.current (which is a Rails extension of Ruby's native Time class)

"Returns Time.zone.now when Time.zone or config.time_zone are set, otherwise just returns Time.now."

so 3.days.ago, for example, is in the application's configured timezone (if it's configured).