If you look a couple of lines above there's this:

``` ruby
# Test DateTime column and defaults, including timezone.
# FIXME: moment of truth may be Time on 64-bit platforms.
if bob.moment_of_truth.is_a?(DateTime)
```

Which dates back to db69c9c when we used to fallback to using `DateTime` when the range of valid `Time` values was limited. This is no longer the case for Rails 4.0+ - it should always be a `Time` so I doubt even if this block of code is being tested.