Automatically switch fields or values of fields

I was wondering if it was possible to change the value of a certain field based on a date, or if it was possible to hide or show a question based on the date.

For example: I am trying to set up registration for an event. There are two different fee rates depending on the date of registration. Early-bird registration and advanced registration. Early-bird rates are only valid until “Date A”. After “Date A” the rates for advanced registration need to be charged. Is there an automated way to do this?

Thank you