Ah! I discovered that this bug wasn't specific to CI at all! It was because the "one-by-one" specs `script/test_all` use NO_COVERALLS=1, and Coveralls is the dependency that ends up requiring Date! When I run it locally, I get the exact same error, and this makes a lot more sense. So we can just move the `require 'date'` to our spec file, and it should be fine.