Historically, searching for Mersenne primes has been used as a test for computer hardware.
The new prime remained unnoticed until routine database maintenance took place months later.
The official discovery date is the day a human took note of the result.
You'll need a reasonably modern PC and the free software at — In 2008, M(37156667) was discovered, and after 8 years GIMPS has finished checking and double-checking every smaller Mersenne number.
With no new, smaller primes found, M(37156667) is officially the "45th Mersenne prime".
Andreas Hoglund and David Stanfill each verified the prime using the CUDALucas software running on NVidia Titan GPUs.