Time-scale Issues

#1
So I recently started a story and it is set a little bit in the future. The problem that I am now having is the concern of whether or not to take out the date that was used for a flash back and instead leave it blank. The reason for this concern is the fact that with the initial planning stages for the plot, I can't determine where it will end up...only that there will be an end. I have so much ideas for material running through my head that I don't know if my story will be complete by the time the real world time reaches that point. Should I leave it be and just work on the story or should I scrap the date for the flash-back and just leave the year summary of when it happened?