What I'm going to say is: technology. The calendar will never change because of technology. This would be the most expensive and extensive change in history. Every computer system, program, device everything.
And you have to either retroactively change past dates, or support 2 systems at the same time. It's almost insurmountable at this point.
No, I didn't.
This is akin to calling the police for the murder of your spouse BEFORE you commit the murder. There's literally no good reason not to wait until after.
Please, name me a logical reason why, before you commit the act, during the planning stage, or even when you are moments from planning to execute the plan, you would call someone entirely unrelated to prepare a document about what you are going to do, instead of calling them AFTER.