This would be interesting if it was intergrated into the game, as a way for controlled mutual wars (if there was an ingame declare war option for example).

I believe that this could create issues out of nothing.

What if a leader doesnt get a message?
What if a random date given isnt a good one and puts someone at a horrible disadvantage?
What if a leader is attempting to be sneaky, and claim a date given isnt actually the date they recieved?
Even better, what if a date is given and is was accidently misread?