Is it possible to create a custom field for customers to sort products on?

Hello! We sell antiques and we would like to be able to sort on the age of the item. Is there any way to create a custom field for the year the item was made and make it possible for customers to sort on that? We are using the debut theme. Our site is still a work in progress.

You can tag each item with a year.

We have a brand filter on the category pages that relies on the tag.

I’m just unsure how to add it to the search screen. I would like to add this too if someone knows the answer.

This the code from the categories page I believe.