Yeah that was my assumption but I've never seen that specific time frame proposed and it just seems like the kind of thing I would have heard of if it was a know fact.
You can estimate this because there is a known amount of energy around in the visible universe (energy, mass, etc.). We know from inflation that this number changes at a given rate. We also know that time and entropy are connected, so when entropy of the known universe is at the maximum, it would be essentially meaningless to say time could continue, i.e ‘the end of time.’
Is this true?? I've never heard this claimed before.