Comment by sigmoid10

These probability shifts would only account for the final output layer (which may also have some shift), but I expect the largest shift to be in the activations in the intermediate latent space. There are a bunch of papers out there that try to get some offset vector using PCA or similar to tune certain model behaviours like vulgarity or friendlyness. You don't even need much data for this as long as your examples capture the essence of the difference well. I'm pretty certain you could do this with "historicalness" too, but projecting it into the future by turning the "contemporaryness" knob way up probably won't yield an accurate result. There are too many outside influences on language that won't be captured in historical trends.