Once per month, Microsoft releases bug fixes and new features for the computer’s operating system. This action is called “patching”; as in patching a hole or vulnerablity.
These patches are released on the second Tueday of the month from America.
Here in South Africa, that is early morning Wednesday.
That is why you awaken on a Wednesday morning, to see that your computer needs an update.
If however, Microsoft discovers a severe security vulnerablity, the patch to fix this will be released almost immediately in order to protect your computer’s operating system.