Windows Phone 7.8 is about to stop supporting
Most people will switch to new phones running Windows Phone 8.1 instead of continuing to use devices that are too old.
The list also shows that Windows 7 operating system ( currently installed on most computers ) will also run out of support on January 13, 2015. Extended support will end on January 13, 2020.
Calendar stopped updating for Windows Phone 7.8 and Windows 7
Are you still using a Windows Phone 7.8 device and do you plan to upgrade to a Windows Phone 8.1 product?