Each game is weighted equally regardless of the day it was played.
Games are weighted based on the day they were played. The value of games on each day are given by a line through the origin and a slope you provide. Games on the last day are equal to the slope while games on any other day are the slope multiplied by the percent of days in the season that have passed.
Weights are equal to the log of (1+the percent of days in the season that have passed). Therefore, the weight on the first day of the season is equal to log(1) and the weight on the day you rank the teams is equal to log(2). The weights on the days between take the shape of a log curve.
The season is divided into equal sized intervals, according to the days in the season, with a game in each interval weighted the same. The weights used in each interval are provided by you.