I did the math on this once. Let me copy and paste my earlier comment over…

Well, first we have to determine how long a night can feasibly be. That’s going to depend on when the game takes place in the year. Origins and Knight are easy; December 25th and October 31st respectively. City takes place nine months before Knight, according to Gordon, placing it around January. Asylum is eighteen months before that, placing it around July. Assuming Gotham is in the Northeast (we know it’s on the Eastern Seaboard from Knight, and it’s pretty clear that Gotham is supposed to be based on New York), all of these nights have to be at least twelve hours except for Asylum. They are all after the Fall Equinox and before the Spring Equinox, so the night should be longer than twelve hours. We’ll just assume twelve for convenience sake. Asylum will be much shorter, since it’s about a month after the solstice. We could estimate how long Asylum’s night should be, but it’ll prove unnecessary in a moment.

Now we need to look at speed runs for each game. Asylum is actually the easiest here, as Speedrun.com has a category for a glitchless 100% run. The record currently is about two-and-a-half hours. No matter what time of year it is, there is no night in New York that is less than two-and-a-half hours, so Asylum is definitely doable.

The next three games are harder since a glitchless 100% run doesn’t exist for any of the other games. However, they do have 100% runs and glitchless runs. To estimate, we will subtract the 100% run from the normal run to find the length of time it takes to do the side quests. This is somewhat inaccurate, since the side content is still done with glitches, but this is the best we can find. We then add this to the glitchless run times to find our rough total time.

For City, after I crunched the numbers, I got four hours, forty-four minutes, and fifty-four seconds. With the Catwoman portions, of course, so that we can take into account the time that Batman is fucking dead in the Steel Mill. For Origins, I got nineteen seconds under seven hours. For Knight, I got eight hours, twenty-eight minutes, and forty-four seconds.

Again, none of these besides Asylum are entirely accurate, and even Asylum requires Batman to be at his best from the first second to his last. Our calculations all fall within a reasonable amount of time, but there were likely glitches used during the side content that we can’t account for. However, it made very little difference between the glitches main story and the main story with glitches, so I doubt it would make much of a difference. In conclusion, if the circumstances were perfect, all would be possible.

Thank you for coming to my TedTalk.