Read more: http://www.neowin.net/news/windows-1...-calendar-apps
A new build of Windows 10 has leaked and with it comes new mail and calendar apps. As you can see from the image in this post, the UI has been overhauled.
It should not come as a big surprise that these apps have been updated as Microsoft has overhauled nearly ever aspect of Windows 10. The new UI represents Microsoft's more modern but less metroy style.