At exactly seven o'clock next Saturday evening, writers, actors and directors will get together to begin a process that's often compared to "bungee jumping for artists".
Teams will be formed, playwrights will put pen to paper - and by five the next morning, have a completed script - before directors and technicians will, in just an hour, develop their concept before actors arrive for a single rehearsal.
Mudlark artistic director, and previous ONE DAY actor and director, Cheyne Mitchell said the annual event is set to celebrate its 20th instalment of "defying impossibility".
"It's lightning in a bottle," she said.
"You never know what you're going to get. I remember years where I was in an opening scene in a rusted clawfoot bath full of water in a suit, and another when I was doing a duologue in front of a Christmas tree.
"That's the magic of it - you end up with all sorts of mania and beauty because it's a different process to anything you've ever done and I think that's why it's continued for so long."
Since its first iteration in June 2004, there have been 123 new plays created by more than 200 individual artists under the banner of ONE DAY, and this year at least six more will be added to the mix.
The teams of artists are picked from exciting writers, directors and actors who have worked throughout the year in Launceston, with the end product to be performed at the Earl Arts Centre in a leap of faith to their dramatic skills.
"It's bonkers and electric and exciting and thrilling," said Jane Johnson, Mudlark Theatre's artistic associate and a ONE DAY veteran who has been involved from the very first event.
"At the time when it launched, it was really about trying something new and getting people together on a mass scale, and the beautiful collaboration that happens when you do that with artists."
Created out of a desire to get graduates from the UTAS theatre degree straight into creating, talking - "and panicking" - together, ONE DAY was created by the now-Princess Theatre's programs manager Stuart Loone, who curated the event for a number of years before it was taken under the auspice of Mudlark in 2006.
"It's overwhelming that it's still going; you don't start something thinking it'll still be here in 20 years time," Mr Loone said.
"It's wonderful that it's still fulfilling something in this very rich artistic community every year."
ONE DAY 20 will run at the Earl Arts Centre from 7pm on Sunday, November 26, at the Earl Arts Centre. Tickets are available at the Theatre North website.
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