Ruth -
You could as a NAME but you are going to limit yourself in the query(s).
That name is meaningful to you but what if your needs change to AsOf2020 or AsOf1989.  See what I mean.

You are better off setting it up more generically so that it is flexible and you don't have to build a ton of queries each time your need change.  See the Query Criteria and Value From a Form videos for examples.