Unus Annus was a YouTube channel launched in 2019 by creators Markiplier and CrankGameplays, built around a single rule: every video would be deleted after exactly one year. The project ran for 365 days, with new videos arriving daily, and ended in November 2020 when the channel itself was removed as planned. Clips of its intro survived through reuploads, reaction videos, and soundboards, and fans still use the sound to mark endings, anniversaries, and the passage of time.