PERTH'S historic Toyota AFL Grand Final will have a twilight start in the west, with the first bounce locked in for 5.15pm local time.

It means the game will start at Optus Stadium at 7.15pm in eastern standard time, which is 15 minutes earlier than last year's start time. 

However, with the game back to normal length quarters in 2021 it will see the clash finish at approximately the same time as the 2020 decider which was held at the Gabba in the first year of the game having to be relocated from Melbourne due to COVID-19.

The AFL last week confirmed Optus Stadium would host this year's Grand Final on Saturday, September 25, with the winners of this weekend's preliminary finals to have a bye week ahead of the pinnacle game. 

The League said the start time for this year's Grand Final had taken into account the audience around the country. 

"The 5:15pm AWST / 7:15pm AEST start time aims to provide fans at the game with the ultimate Grand Final experience by maximising the stadium's offering while taking into consideration the broadcast audience across the country," the AFL's general manager of clubs and broadcasting Travis Auld said. 

"The AFL, together with the Seven Network, remain cognisant of finishing the match at a suitable time for younger footy fans and, as a result, landed on a timeslot that is earlier than the usual start time for night matches during the season and last year’s Grand Final.

"Historically, a really special part of Grand Final day is the build-up and anticipation, and we want to ensure we can share the excitement and atmosphere with the millions watching across the nation and around the world."

Melbourne and Geelong will meet at Optus Stadium on Friday night in the first preliminary final before Port Adelaide and the Western Bulldogs lock horns at Adelaide Oval on Saturday night in a bid to clinch a Grand Final berth.