How long does winter last?

Winter in Endless Legend has a pretty strong negative effect on food and production:

all Food and Dust producing land will produce one less Food

Leading me to wonder how the length of winter is calculated.

Is the formula or any of the variables know about how the length of winter is calculated?

Is the length of winter or onset time random, fixed, or event determined?

Or perhaps is the onset of winter based purely on the length of the game and the current turn?

The wiki says this:

Every winter is longer than the one before, and adds one new penalty (written in red at the beginming of the winter).

I couldn't find any consistent information about winter duration, but I read that after you won the game, the winter becomes eternal. It is by design.

There is a part of the widget in the bottom-right corner that when you hover over it, the sub-widget tool-tip will give you a prediction on when winter is coming.

As @aslum notes, there are one or more techs that allow you to improve the predictive capabilities of the winter guess.