Update: Please also check the comments on WPCentral according to this problem: http://www.wpcentral.com/native-calendar-app-windows-phone-81-updated
Update 2: I got a reply from MS support according to this problem on a developer forum: They are aware of the problem and working on a fix, please see: http://social.msdn.microsoft.com/Forums/wpapps/en-US/e1fd72b7-66c3-44f5-b58d-84766eace215/info-major-bug-in-the-wp-internal-calendar-after-last-update?forum=wpdevelop
This morning my phone was showing 10 updates, which included some apps from microsoft like the bing health&fitness app and also the windows phone internal calendar app.
Since installing this update the windows phone internal calendar app has a major bug: Creating a new appointment or editing an existing appointment crashes the app.
Important: This bug has nothing to do with Week View.
It occurs, when you try to create a new appointment in the WP internal calendar app.
This problem occurs on my phone and I got some error reports about it from users.
Background: The windows phone programming interface provides a „SaveAppointmentTask“.
This task is used by the WP internal calendar app and also by third party apps to create appointments.
It seems that the problem occurs in this task.
As a result, all (!) calendar apps that use this task share this problem.
Although this problem has nothing to to with Week View I already got some error reports about and I am afraid that they will get even more, once this update of the WP internal calendar is installed on more windows phones. 🙁
If you experience this problem, please try to create an appointment with the WP built in calendar.
Please tell me, if this problem occurs on your pone too.
I really hope, MS will fix this as soon as possible.