We all used the in game timer provided by dying light.

My run (player 1) starts at 19:44 and ends at 39:47 (including the pvp fight where It shows the final timer end screen) Before that point we did some failed attempts so thats why the official run starts at 19:44. Here is teh video proof:

Joemalonthegreat (player 3 ) run also uses the in game timer. His run starts at 0:27 and ends at 20:34 (where he also shows the end game final timer screen after the pvp fight). Here is his video prrof:

Blinks run (player 2 ) also uses the in game timer. His run starts at 0:23 and ends at 20:25 (where he also includes the final end timer screen) Here is the video proof: