So guys I and my team have been working on a horror story. Mid way through the story a point comes where it takes 500+ days for a major event to take place in the story (Climax).
The real problem comes now - Since it being a horror we have to show the horror taking place in the protagonists life as well as cover the 500 days. So my concern is how do we move forward and make it intriguing ?
Just really simplify the approach for yourself by thinking about what is the most important aspect of these 500 days. If it's "After 500 days, we had no food left and half of our group had starved," then the most important aspect there is the RESULT, the consequence of those 500 days. In that case, I would flash forward and have a title come up, "500 days later," and show the characters as starving and emaciated.
Now, if this scenario is more like: "we fought off hoards of demons for 500 days straight," well then, you will need to show these battles and the non-stop struggle in a montage, or series of important scenes, because the most important thing here is the battles and struggles they faced DURING the 500 days.
Just think about what inspires you the most out of the "500 day," context. Is the experience during those 500 days, or the result AFTER the 500 days? And like the member said in a reply above, use flashbacks, or flashforwards, OR use a title that pops up and just skip the 500 days and have a character explain what has happened, or just SHOW what has happened.
Just think about what is important for your story, and how to show it on screen without showing the audience too much, or boring them. Show the juicy bits, and have it presented in appropriate moments.