Maybe an example of the failure this detects helps: when I used to work on Rails apps in the olden days it was easy to call Time.now and get the local time instead of Time.zone.now to get UTC time. This often lead to wrong dates but tests would only fail once it was a new day in UTC land but still the old day in the local time zone. Making the CI machine's system time something Fiji time really helped in getting failures much sooner after changes were pushed.