Evidence of mysterious 'recurring nova' that could reappear in 2024 found in medieval manuscript from 1217

"dramatically increases in brightness for about a week every 80 years. But it has been scientifically documented only twice — once in 1866, and again in 1946. (The star’s next long-awaited flare-up is expected in 2024)."

Am I being stupid here? Why does it jump to 78 years to be expected 2024?
 
Mar 24, 2024
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"dramatically increases in brightness for about a week every 80 years. But it has been scientifically documented only twice — once in 1866, and again in 1946. (The star’s next long-awaited flare-up is expected in 2024)."

Am I being stupid here? Why does it jump to 78 years to be expected 2024?

T CrB oubursts only happen about once every 80 years, the last was was back in 1946. "We know that before it goes nova it dims for about a year, and T Coronae Borealis started dimming back in March 2023, so that's why we think it's going to go nova between now and the end of September." So it has been dimming for just about a year at this point which means that the fireworks should happen soon.