Time#to_f

gistfile1.txt

[1] pry(main)> RUBY_VERSION
=> "2.0.0"
[2] pry(main)> require 'active_support/time'
=> true
[3] pry(main)> Time.new(2013, 4, 1).end_of_day
=> 2013-04-01 23:59:59 +0900
[4] pry(main)> Time.new(2013, 4, 1).end_of_day.to_f
=> 1364828400.0
[5] pry(main)> Time.at(1364828400.0)
=> 2013-04-02 00:00:00 +0900
[6] pry(main)> Time.gm(2013, 4, 1, 23, 59, 59).to_i
=> 1364860799
[7] pry(main)> Time.gm(2013, 4, 1, 23, 59, 59).to_f
=> 1364860799.0
[8] pry(main)> Time.gm(2013, 4, 1, 23, 59, 59, Rational(999999999, 1000)).to_i
=> 1364860799
[9] pry(main)> Time.gm(2013, 4, 1, 23, 59, 59, Rational(999999999, 1000)).to_f
=> 1364860800.0

https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/time/calculations.rb#L177