War Council no visible countdown. PS4

It sounds like the number is such a large negative number that the game cannot display it. If setting it to Dec 31 2099 still leaves 6 years, then you should set it for 2109 if you can. That is the only work around that I know of. The time to complete is just a simple calculation of the current time compared to the time stamp of when the operation was started, which there is no way to adjust on a console. The only option I know of is setting the system clock forward to force completion of the operation. If PS4 won't let you set it that far forward, your only options are reload before the problem happened, live with it, or start a new game if you can't do either of those.