The Trail Time and Resting Time Calculator can be found through the Idita-Type 2016 article in the Musher section. It is a simple Google Sheets page that the Mushers use to find out important information for the Trail Log.
Mushers enter the number of miles their team traveled in a day. The spreadsheet divides that number by an average rate of 5 mph to determine the number of running hours. The resting time is the difference between a 24 hour day and the number of running hours on the trail.