Failures for by_star only occur (seemingly) in a positive timezone where the local time is in a day in the future from UTC.
So in +1000 (Brisbane) these three specs only fail BEFORE 10am. After 10am it's a sea of wonderful green.

..................................F..F..F...................................

1)
'Post today should show the post for tomorrow' FAILED
expected ["Today's post", "Today"] to include "Tomorrow's post"
./spec/by_star_spec.rb:197:

2)
'Post yesterday should be able find yesterday, given a Date' FAILED
expected ["Today's post", "Today"] to include "Yesterday's post"
./spec/by_star_spec.rb:213:

3)
'Post tomorrow should be able find tomorrow, given a Date' FAILED
expected [] to include "Tomorrow's post"
./spec/by_star_spec.rb:230:

Finished in 0.263454 seconds

76 examples, 3 failures