My guess is that if you need to have been there for 5y, you need to have a way to tell when that 5y starts. I presume it only matters if you apply the day after

My guess is that if you need to have been there for 5y, you need to have a way to tell when that 5y starts. I presume it only matters if you apply the day after 5y. When I applied I had been in the UK for over 10y, provided 10y worth of proof of address, and the issue never came up.