good solution

This failure solution in this case:

Test.expect(elapsed_seconds((Time.now - 30), Time.now) == 30)

Fair enough, guess I was overthinking

The Kata description explicitely states: "The start time will always be before the end time."

Also AM/PM has nothing to do with this. "Time is stored internally as the number of seconds with fraction since the Epoch, January 1, 1970 00:00 UTC"

I don't think this would work if there were more test cases ._.
First instance of an AM/PM where the start_time >= than the end_time for example

oh dear, and to think it was just this easy all along XD

Didn't know that hashes could be manipulated that way!

I personnaly prefer map/reduce because its how I learned the concept, from big data map/reduce

It never gets added. The way join works is it just joins the elements using the given character, doesn't append after each one.

http://www.ruby-doc.org/core-2.1.2/Array.html#method-i-join

looks good, but I'm not sure I can
read where in the code, the final
comma gets chopped off. Hmmm.

Good for beginners (like me) to learn this.

In ruby, map and collect are synonymous, which one you use is based purely on preference.