make s.date into a Date object (not a string)

fix for this error I am getting:
23:54:34 ++ ruby -I vendor/gems/bundler/lib vendor/gems/bundler/bin/bundle exec rake db:rebuild
23:54:35 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:35 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:35 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:35 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:35 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:36 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:36 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:36 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"
23:54:36 Invalid gemspec in [/var/lib/jenkins/gems/job-peacock_sandbox-5659/specifications/spork-1.0.0rc2.gemspec]: invalid date format in specification: "2012-02-08 00:00:00.000000000Z"