If you have a Windows Phone and there is an OEM app that you want to remove but you can’t seem to figure out how to do it, there is a simple trick that allows you to remove any application.
If you take a look at the video below, by setting the year on your phone to 2115 and changing the time zone to Amsterdam, you can then uninstall any application on the device, including the calendar.
We should warn you that this should only be done if you really dislike an application from an OEM as there is only one known way to get the application back, that’s using SysApp Pusher. If you hit the buy link in the image shown above, it takes you to the Windows Phone store to re-download the application but if you remove the app, you won't be able to access the 'buy' link.
This is certainly an odd bug, glitch, feature, or whatever you want to call it but seeing that it requires a certain set of parameters to be aligned to allow for the uninstall, it would seem intentional.
We have confirmed that this works on Windows Phone 8.1 devices and it is said to work on Windows Phone 8 devices as well. So there you go, want to uninstall an OEM app? Follow the direction in this post and you can do so.