fog/fog — pull request #2514 by fcheung (2013-12-27 10:41:09+00:00)
Title: [AWS|EC2] request_spot_instances.rb requires that date parameters be iso...

Time#iso8601 does appear to be in 1.8.7 after all http://ruby-doc.org/stdlib-1.8.7/libdoc/time/rdoc/Time.html#method-i-iso8601