Microsoft introduced a new modern-style calendar in Windows 10 to create more consistency on the desktop (which also got redesigned with a dark theme and other visual improvements), but the old-style version was still available with a registry tweak.



Certainly, this came in handy to those who got used to the old calendar, especially because it popped out much faster than the modern version, but it appears that Microsoft’s making a change in Windows 10 Redstone that would only allow you to use the new flavor.
As WinAero spotted, the latest Windows 10 Redstone preview build, namely version 14291, blocks the registry tweak that enabled the original design of the calendar, so even if you turn to this trick, it has absolutely no effect on your desktop and you still get the modern interface.
Microsoft’s decision is not surprising at all given the fact that the company’s working to make everything in Windows 10 look and feel modern, so it was probably just a matter of time until this happened.
The desktop Control Panel also going away In addition to the old-style calendar, the transitional Control Panel is also going dark and the Redstone update is very likely to be the moment when Microsoft will remove it completely.
Control Panel will be replaced with Settings, a new app that offers support for touch devices as well and which is available on Windows 10 Mobile smartphones too with a similar look and feel.
Moving Control Panel to Settings is just a matter of time and options are slowly migrated with new builds, and by the time Redstone lands in stable form, the transition should be complete.
Without a doubt, Microsoft’s aiming for a modern desktop in Windows 10 Redstone, so expect the old-style elements that have been around since Windows XP to disappear when this update lands in the summer.