Hello,
This is calculated every time Factorio starts. In the information tab, what I meant there is it can't be changed while the game is running. For example, you can open the pause menu, go into mod settings, and change daylength even as the game is running. You don't need to quit out and reload, it takes effect as soon as the setting is changed.
Daylength requires nothing. Accumulator capacity requires a full Factorio restart. But not a new save.
Now with that out of the way... Let's talk Krastorio 2.
I went through K2's files, and it modifies vanilla accumulators at a stage where Clockwork's modifications could have happened before it. Meaning, basically, Clockwork makes the change, and then Krastorio 2 overwrites it with its own change.
I'll upload a fix for this when I have a minute.