"The date Marty McFly went back in time" is October 25th (technically 26th), 1985, so for the 25th anniversary this year there's all sorts of hoopla.
For example, check out this tie-in for the Spike (TV) Scream Movie Awards, where they're staging a cast reunion:
It's a shot-for-shot remake of the original teaser trailer! Great job, Spike!
Also, AMC Theatres is doing a limited release of the 25th anniversary digitally-remastered edition in select markets in the US next Saturday and Monday, and I am planning on road-tripping out to see it, the nearest participating market to me is at least an hour's drive http://www.amctheatres.com/bttf