Help me to understand physics cache UI

[raincole]

I were simulating a skirt. But when I pause the animation, the cache is immediately “outdated”:

I didn’t change anything physics settings. In face I didn’t change anything: it said outdated right after it’s simulated.

Also my timeline looks like this:

What are these “gaps”?

[Okidoki]

You was just running the sim (maybe with skip frames settings) and not baking it?