Ruby date equation not returning expected truth value

Question

Why do the following differ?

Time.now.end_of_day      == Time.now.end_of_day - 0.days      # false
Time.now.end_of_day.to_s == Time.now.end_of_day - 0.days.to_s # true

Answer 1

Because the number of nanoseconds is different:

ruby-1.9.2-p180 :014 > (Time.now.end_of_day - 0.days).nsec
 => 999999000 
ruby-1.9.2-p180 :015 > Time.now.end_of_day.nsec
 => 999999998 

Answer 2

Like Mischa said, the times differ by nanoseconds. Here is an article on workarounds and fixes for doing this in Rails, specifically for tests like you are doing.

The seemingly most straightforward approach given is to round the times to seconds by appending .to_i, but there are other alternatives.