One of iOS 7.1’s major changes was a new Calendar app that added such features as the ability to see a full list of events while in your Calendar’s month view, as well as a more complete list of nation-specific holiday.
If you use your iPhone as an organizer, the new Calendar app is enough to update to iOS 7.1 on its own right. Unfortunately, iOS 7.1 also broke the popular evasi0n jailbreak, meaning that to get the new Calendar, you had to abandon your jailbroken device.
No longer. If you have a jailbroken iOS device, you can now download a new app that patches the iOS 7.1 calendar into iOS versions 7.0 and 7.0.6. Called Gregorian, it can be downloaded through Cydia from the http://rpetri.ch/repo/ repository.