WTF arithmetics

gistfile1.txt

t = Time.now
wtf = 2.years

puts wtf.to_i             #=> 63115200
puts ((t + wtf) - t).to_i #=> 63158400

It seems that the problem is that wtf is float and the arithmetic is done in floating point.

Forcing wtf to integer yields the right result

puts wtf.class # => Float

puts t + wtf.to_i - t #=> 63115200.0

Surprise! The last result is Float too! It seems that the principle of least surprise is not followed here!

Not really. I found that time arithmetics take into account the leap years, the daylight saving zones and other time anomalies.
2.years returns a Duration object (http://github.com/rails/rails/blob/master/activesupport/lib/active_support/duration.rb) mimicking a float:

year = ActiveSupport::Duration.new(365.25.days, [[:years, 1]])
year.class  #=> Float. Surprise!

so t + 2.years is actually different than t + 2.years.to_f, some coercion magic is happening there.

Lesson learned: You think you know how to count time. Think twice =S