Question

I’m looking for an efficient way, in Ruby 1.9.x/Rails 3.2.x, to iterate between two DateTime objects, with a one-hour step.

('2013-01-01'.to_datetime .. '2013-02-01'.to_datetime).step(1.hour) do |date|
   ...
end

I understand that an issue with this is that 1.hour is just the number of seconds, but my attempts to convert that to a DateTime object and use that as the step doesn’t work either.

I looked at “Beware of Ruby Sugar“. It mentions, near the bottom, that DateTime has a direct step method. I confirmed this by running methods on a DateTime object, but I cannot find any documentation on step in DateTime, in either Ruby’s or Rails’ documents.

Answer 1

Similar to my answer in “How do I return an array of days and hours from a range?“, the trick is to use to_i to work with seconds since the epoch:

('2013-01-01'.to_datetime.to_i .. '2013-02-01'.to_datetime.to_i).step(1.hour) do |date|
  puts Time.at(date)
end

Note that Time.at() converts using your local time zone, so you may want to specify UTC by using Time.at(date).utc