Validation conditions for dates and birthday

Hi all
I have several question in which the answer should be the year of a disease diagnosis. I wanto to place two validation condition: just 4 digits, because the years have 4 digits, and also that the year be the current or any in past, never in the future.

I want to place a validation condition in the current date. The date is my first question and is about the date (today) in which the form is filled. I want to be sure that the date is the current date and not some past or future date.

I wanto to place a validation condition in the birth day question. I want to be sure the birth day is a date in the past not in the future nither today.

Thank you very much for the support!