00_README.md

A benchmark comparison between DateTime and Time in Ruby.

Instructions

This uses the excellent benchmark-ips library by Evan Phoenix. You'll have to install that with:

gem install benchmark-ips

To do the Rails comparisons, you'll need to be within a Rails environment. The easiest thing would be to save the benchmark script into a Rails project, make sure benchmark-ips is in your Gemfile, and then enter a rails c environment. In the console, enter:

require_relative "01_benchmark"

This assumes you saved the benchmark in your Rails.root directory as 01_benchmark.rb.

01_benchmark.rb

require "time"
require "benchmark/ips"

puts "Ruby version: #{RUBY_VERSION}"
puts "Rails version: #{Rails.version}" if defined?(Rails)
puts

Benchmark.ips do |x|
	x.report("DateTime.now") { DateTime.now }
	x.report("DateTime.current") { DateTime.current } if DateTime.respond_to?(:current)
	x.report("Time.now") { Time.now }
	x.report("Time.current") { Time.current } if Time.respond_to?(:current)

	x.compare!
end

02_output_outside_rails

Ruby version: 2.4.2

Warming up --------------------------------------
        DateTime.now    81.286k i/100ms
            Time.now   127.296k i/100ms
Calculating -------------------------------------
        DateTime.now      1.065M (± 4.2%) i/s -      5.365M in   5.044399s
            Time.now      2.033M (± 4.6%) i/s -     10.184M in   5.019910s

Comparison:
            Time.now:  2033095.1 i/s
        DateTime.now:  1065467.5 i/s - 1.91x  slower

03_output_within_rails

Ruby version: 2.4.2
Rails version: 5.1.4

Warming up --------------------------------------
        DateTime.now    78.277k i/100ms
    DateTime.current     7.153k i/100ms
            Time.now   125.190k i/100ms
        Time.current    28.140k i/100ms
Calculating -------------------------------------
        DateTime.now    990.235k (± 6.3%) i/s -      4.931M in   4.999849s
    DateTime.current     79.184k (± 4.4%) i/s -    400.568k in   5.068635s
            Time.now      1.982M (± 9.7%) i/s -      9.890M in   5.032807s
        Time.current    302.531k (± 4.6%) i/s -      1.520M in   5.033420s

Comparison:
            Time.now:  1981824.3 i/s
        DateTime.now:   990234.5 i/s - 2.00x  slower
        Time.current:   302530.8 i/s - 6.55x  slower
    DateTime.current:    79184.0 i/s - 25.03x  slower