These probably appear because that field is a datetime. If you convert it to just a date, without the hours and minutes available, they won't appear in the filtering options. There are a few ways to accomplish this--you may be able to right click on the field name and just choose date, or you may write a calculation to convert/truncate it.
Here are the Date functions you have access to:
Awesome thanks Matthew, that was easy!
Any ideas on removing the options to select future dates?
Yes--in your filter options, check "Only Relevant Values". As long as no future dates exist in your data source, this solves that problem.