In Windows Phone 8.1 certain core services have changed in that they can be updated dynamically, bypassing the requirement for a full-fledged OS update. In theory, that should allow Microsoft to respond to the rapidly changing market by delivering faster paced, piecemeal updates. In reality, it also increases the chances that something may go wrong, and that is exactly what has happened.
Last night Microsoft pushed out a rare update for the calendar app, which was disentangled from the OS in 8.1, much like Xbox Music. The update brought the version number to 1.0.14127.246 and there was no changelog. Although it is exasperating to users to have to update an app without knowing what changed – or improved, it is even more vexing when that update breaks something.
Immediately following the update, people in comments started to complain that the attempting to create or edit an appointment caused the calendar app to crash. We have tested the update on various devices, including the Lumia 630 with the Lumia Cyan firmware, and they all have the same problem, rendering the calendar app a view-only tool.